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• SQL-Join with NULL-columns

  - by tstenner

  I'm having the following tables: Table a +-------+------------------+------+-----+ | Field | Type | Null | Key | +-------+------------------+------+-----+ | bid | int(10) unsigned | YES | | | cid | int(10) unsigned | YES | | +-------+------------------+------+-----+ Table b +-------+------------------+------+ | Field | Type | Null | +-------+------------------+------+ | bid | int(10) unsigned | NO | | cid | int(10) unsigned | NO | | data | int(10) unsigned | NO | +-------+------------------+------+ When I want to select all rows from b where there's a corresponding bid/cid-pair in a, I simply use a natural join SELECT b.* FROM b NATURAL JOIN a; and everything is fine. When a.bid or a.cid is NULL, I want to get every row where the other column matches, e.g. if a.bid is NULL, I want every row where a.cid=b.cid, if both are NULL I want every column from b. My naive solution was this: SELECT DISTINCT b.* FROM b JOIN a ON ( ISNULL(a.bid) OR a.bid=b.bid ) AND (ISNULL(a.cid) OR a.cid=b.cid ) Is there any better way to to this?

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• Problem with pointer copy in C

  - by Stefano Salati

  I radically re-edited the question to explain better my application, as the xample I made up wasn't correct in many ways as you pointed out: I have one pointer to char and I want to copy it to another pointer and then add a NULL character at the end (in my real application, the first string is a const, so I cannot jsut modify it, that's why I need to copy it). I have this function, "MLSLSerialWriteBurst" which I have to fill with some code adapt to my microcontroller. tMLError MLSLSerialWriteBurst( unsigned char slaveAddr, unsigned char registerAddr, unsigned short length, const unsigned char *data ) { unsigned char *tmp_data; tmp_data = data; *(tmp_data+length) = NULL; // this function takes a tmp_data which is a char* terminated with a NULL character ('\0') if(EEPageWrite2(slaveAddr,registerAddr,tmp_data)==0) return ML_SUCCESS; else return ML_ERROR; } I see there's a problem here: tha fact that I do not initialize tmp_data, but I cannot know it's length.

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• How to delete a Dictionary row that is a Double by using an Int?

  - by Richard Reddy

  Hi, I have a Dictionary object that is formed using a double as its key values. It looks like this: Dictionary<double, ClassName> VariableName = new Dictionary<double, ClassName>(); For my project I have to have the key as the double as I require values like 1.1,1.2,2.1,2.2,etc in my system. Everything in my system works great except when I want to delete all the keys in a group eg all the 1 values would be 1.1,1.2, etc. I can delete rows if I know the full value of the key eg 1.1 but in my system I will only know the whole number. I tried to do the following but get an error: DictionaryVariable.Remove(j => Convert.ToInt16(j.Key) == rowToEdit).OrderByDescending(j => j.Key); Is there anyway to remove all rows per int value by converting the key? Thanks, Rich

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• Creating a 2d matrix from an array (java)

  - by anna

  I'm supposed to write a method that creates a 2d matrix from an array, for instance: ({1, 2, 3, 4}, 3) should return the matrix {{1, 2, 3}, {4}} public class Matrix { public static int[][]toM(int[] array, int a) { int[][]matrix = new int [(array.length + a- 1)/ a][a]; for (int i = 0; i < array.length; i++){ int value = array[i]; value = value++; for (int row = 0; row < (array.length + a- 1)/a; row++) { for (int col = 0; col < a; col++) { matrix[row][col]= value++; } } } return matrix; } } I'm getting [[4, 5, 6], [7, 8, 9]]?

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• MySQL query with 2 COUNT() of other tables with where conditions

  - by Isern Palaus

  Hello, I've a table called sports that contains a list of list of sports, other called seasons that contains the seasons for a specific sport and competitions that have the competitions of a specific sport and season. I need one MySQL query to print the list of sports with how much seasons and competitions has each. My tables structure: sports +--------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | name | varchar(32) | NO | | NULL | | | slug | varchar(45) | NO | | NULL | | | description | varchar(128) | NO | | NULL | | +--------------------+------------------+------+-----+---------+----------------+ seasons +--------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | id_sport | int(10) unsigned | NO | MUL | NULL | | | name | varchar(32) | NO | | NULL | | | slug | varchar(32) | NO | | NULL | | +--------------------+------------------+------+-----+---------+----------------+ competitions +--------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | id_season | int(10) unsigned | NO | MUL | NULL | | | name | varchar(32) | NO | | NULL | | | slug | varchar(64) | NO | | NULL | | | description | varchar(128) | YES | | NULL | | +--------------------+------------------+------+-----+---------+----------------+ The result of my query needs to contain: sports.*, total_seasons (SUM of seasons where seasons.id_sport=sports.id) and total_competitions (SUM of competitions where competitions.id_season=seasons.id AND seasons.id_sport=sports.id). Thank you in advance!

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• What will happen if I change the type of a column from int to year?

  - by MachinationX

  I have a table in MySQL 4.0 which currently has a year field as a smallint(6) type. What will happen if I convert it directly to a Year type with a query like the following: ALTER TABLE t MODIFY y YEAR(4) NOT NULL DEFAULT CURRENT_TIMESTAMP; When the current members of column y have values like 2010? I assume that because the year type is technically values from 1-255, values above that will be truncated or broken. So if MySQL isn't smart enough to realize that 2010(int) = 110(year), what would be the simplest query or queries to convert the values? Thanks for your help!

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• Why "constructor-way" of declaring variable in "for-loop" allowed but in "if-statement" not allowed?

  - by PiotrNycz

  Consider this simple example: /*1*/ int main() { /*2*/ for (int i(7); i;){break;} /*3*/ if (int i(7)) {} /*4*/ } Why line-2 compiles just fine, whilst line-3 gives the error? This is little strange to me why if-statement is in this aspect treated worse than for-loop? If this is compiler specific - I tested with gcc-4.5.1: prog.cpp: In function 'int main()': prog.cpp:3:7: error: expected primary-expression before 'int' prog.cpp:3:7: error: expected ')' before 'int' I was inspired by this question [UPDATE] I know this compiles just fine: /*1*/ int main() { /*2*/ for (int i = 7; i;){break;} /*3*/ if (int i = 7) {} /*4*/ }

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• C++ Scoping and ambiguity in constructor overloads

  - by loarabia

  I've tried the following code snippet in 3 different compilers (G++, clang++, CL.exe) and they all report to me that they cannot disambiguate the overloaded constructors. Now, I know how I could modify the call to the constructor to make it pick one or the other (either make explicit that the second argument is a unsigned literal value or explicitly cast it). However, I'm curious why the compiler would be attempting to choose between constructors in the first place given that one of the constructors is private and the call to the constructor is happening in the main function which should be outside the class's scope. Can anyone enlighten me? class Test { private: Test(unsigned int a, unsigned int *b) { } public: Test(unsigned int a, unsigned int b) { } }; int main() { Test t1 = Test(1,0); // compiler is confused }

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• how do I check if a c++ string is an int?

  - by user342231

  when I use getline, I would input a bunch of strings or numbers, but I only want the while loop to output the "word" if it is not a number. so is there any way to check if "word" is a number or not, I know I could use atoi() for c-strings but how about for strings of the string class int main () { stringstream ss (stringstream::in | stringstream::out); string word; string str; getline(cin,str); ss<<str; while(ss>>word) { //if( ) cout<<word<<endl; } }

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• C++ pointer to functions, Beginner Question...

  - by BobAlmond

  Hi all, I want to ask about pointer in C++ I have some simple code: int add(int a, int b){ return a+b; } int runner(int x,int y, int (*functocall)(int, int)){ return (*functocall)(x,y); } now, suppose I call those functions using this way : cout<<runner(2,5,&add); or maybe cout<<runner(2,5,add); is there any difference? because when I tried, the result is the same and with no error. Thanks a lot

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• how to make this piece of code work in C++?

  - by cambr

  #include<stdio.h> void print(int *arr[], int s1, int s2) { int i, j; printf("\n"); for(i = 0; i<s1; i++) { for(j = 0; j<s2; j++) { printf("%d, ", *((arr+i)+j)); } } printf("\n"); } int main() { int a[4][4] = {{0}}; print(a,4,4); } This works in C, but not in C++. error: cannot convert `int (*)[4]' to `int**' for argument `1' to `void print(int**, int, int)' Why does it not work in C++? What change is needed to be made?

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• Functions without arguments, with unit as argument in scala

  - by scout

  def foo(x:Int, f:Unit=>Int) = println(f()) foo(2, {Unit => 3+4} //case1 def loop:Int = 7 foo(2, loop) //does not compile changing loop to //case 2 def loop():Int = 7 foo(2, loop) // does not compile changing loop to //case 3 def loop(x:Unit): Int = 7 //changing according to Don's Comments foo(2,loop) // compiles and works fine should'nt case 1 and case 2 also work? why are they not working? defining foo as def foo(x:Int, y:()=>Int) then case 2 works but not case 1. Arent they all supposed to work, defining the functions either way. //also i think ()=Int in foo is a bad style, y:=Int does not work, comments??

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• Scala puts precedence on implicit conversion over "natural" operations... Why? Is this a bug? Or am

  - by Alex R

  This simple test, of course, works as expected: scala var b = 2 b: Int = 2 scala b += 1 scala b res3: Int = 3 Now I bring this into scope: class A(var x: Int) { def +=(y:Int) { this.x += y } } implicit def int2A(i:Int) : A = new A(i) I'm defining a new class and a += operation on it. I never expected this would affect the way my regular Ints behave. But it does: scala var b:Int = 0 b: Int = 0 scala b += 1 scala b res29: Int = 0 scala b += 2 scala b res31: Int = 0 Scala seems to prefer the implicit conversion over the natural += that is already defined to Ints. That leads to several questions... Why? Is this a bug? Is it by design? Is there a work-around (other than not using "+=")? Thanks

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• Shuffle array variables in a pre-specified order, without using extra memory of "size of input array"

  - by Eternal Learner

  Input : A[4] = {0,4,-1,1000} - Actual Array P[4] = {1,0,3,2} - Order to be reshuffled Output: A[4] = {4,0,1000,-1} Condition : Don't use an additional array as memory. Can use an extra variable or two. Problem : I have the below program in C++, but this fails for certain inputs of array P. #include<iostream> using namespace std; void swap(int *a_r,int *r) { int temp = *r; *r = *a_r; *a_r = temp; } int main() { int A[4] = {0,4,-1,1000}; int P[4] = {3,0,1,2}; int value = A[0] , dest = P[0]; for(int i=0; i<4;i++) { swap(&A[dest],&value); dest = P[dest]; } for(int i=0;i<4;i++) cout<<A[i]<<" "; }

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• Stucture with array of pointers in C

  - by MVTCplusplus

  What's wrong with this? Can I have an array of pointers to SDL_Surfaces in a struct in C? typedef struct { int next_wheel; int pos_X; int pos_Y; int front_wheel_pos_X; int front_wheel_pos_Y; int velocity; int rear_wheel_pos_X; int rear_wheel_pos_Y; SDL_Surface* body; SDL_Surface* rear_wheel[9]; SDL_Surface* front_wheel[9]; } mars_rover; ... mars_rover* init_rover() { mars_rover* rover = (mars_rover*)malloc(sizeof(mars_rover) + sizeof(SDL_Surface) * 19); ... return rover; } int main() { mars_rover* rover = init_rover(); ... }

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• How to change the text int JLabel under the while or for loop?

  - by guilgamos

  I want to create a simple clock by using java. The code is very simply that i will give an example shown below for(int i=0;i<=60;i++) jLabel11.setText( Integer.toString(i) ); The problem is while I'm running my program the result didn't show the update in sequence. I mean it show only 60 digit immediately. It didn't show the change from 1 to 2 to 3 ... something like this. How can i fix this problem. Thank you in advance.

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• what is the accepted naming convention for int, string, array, list, object, etc...

  - by RJ

  The company I work for now uses a set naming convention for their C# variables such as iSomeName for int, sSomeName for string, aSomeName for arrays, bSomeName for boolean, dSomeName for datetime and so on. My previous employer did not use the i, s, a, b and d prefixes and just named the variables a good understandable name. My impression is that these prefixes lost favor a while ago and from what I read it is not the current trend. It seems fine to me either way as long as the variable is descriptive enough to understand what it is doing but I was wondering what the now-a-day accepted practice is for naming variables?

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• Why do dicts of defaultdict(int)'s use so much memory? (and other simple python performance question

  - by dukhat

  import numpy as num from collections import defaultdict topKeys = range(16384) keys = range(8192) table = dict((k,defaultdict(int)) for k in topKeys) dat = num.zeros((16384,8192), dtype="int32") print "looping begins" #how much memory should this use? I think it shouldn't use more that a few #times the memory required to hold (16384*8192) int32's (512 mb), but #it uses 11 GB! for k in topKeys: for j in keys: dat[k,j] = table[k][j] print "done" What is going on here? Furthermore, this similar script takes eons to run compared to the first one, and also uses an absurd quantity of memory. topKeys = range(16384) keys = range(8192) table = [(j,0) for k in topKeys for j in keys] I guess python ints might be 64 bit ints, which would account for some of this, but do these relatively natural and simple constructions really produce such a massive overhead? I guess these scripts show that they do, so my question is: what exactly is causing the high memory usage in the first script and the long runtime and high memory usage of the second script and is there any way to avoid these costs?

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• Quick C Style Question

  - by LearningC

  Which is considered better style? int set_int(int *source){ *source = 5; return 0; } int main(){ int x*; set_int(x); } OR int *set_int(){ int *temp = NULL; temp = malloc(sizeof (int)); *temp = 5; return temp; } int main(){ int *x = set_int(); } Coming for a higher level programming background I gotta say I like the second version more. Any, tips would be very helpful. Still learning C.

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• Java Basics: create class object

  - by user1767853

  In C++: class Rectangle { int x, y; public: void set_values (int,int); int area () {return (x*y);} }; int main () { Rectangle rect; rect.set_values (3,4); } In Java: class Rectangle { int x, y; void set_values (int x,int y); int area () {return (x*y);} } public static void main(String[] args) { Rectangle rect=new Rectangle(3,4); } In C++ compiler will create rect object & reserve memory 4 bytes. I want to know How Java is creating object?

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• Tile map collision is not working properly

  - by Sigh-AniDe

  I am having problems setting collision between my sprite and the tiles. I have only done the code for colision for moving upwards but some places on the map it moves up and some places it doesn't. Here is what I have so far: Vector2 position; private static float scalingFactor = 32; static int tileWidth = 32; static int tileHeight = 32; int[ , ] map = { {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }, {0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }, {0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }, {0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }, {0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }, {0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }, }; // This is in turtle.update if ( keyboardState.IsKeyDown( Keys.Up ) ) { if ( position.Y > screenHeight / 4 ) { //// current position of the turtle on the tiles int mapX = ( int )( position.X / scalingFactor ); int mapY = ( int )( position.Y / scalingFactor ) - 1; if ( isMovable( mapX , mapY , map ) ) { position.Y = position.Y - scalingFactor; } } else { MoveUp(); } } private void MoveUp() { motion.Y = -1; } public bool isMovable( int mapX , int mapY , int[ , ] map ) { if ( mapX < 0 || mapX > 19 || mapY < 0 || mapY > 20 ) { return false; } int tile = map[ mapX , mapY ]; if ( tile == 0 ) { return false; } return true; } protected override void Update( GameTime gameTime ) { turtle.Update( screenHeight , scalingFactor , map ); base.Update( gameTime ); }

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• How can I have multiple layers in my map array?

  - by Manl400

  How do I load Levels in my game, as in Layer 1 would be Objects, Layer 2 would be Characters and so on. I only need 3 layers, and they will all be put on top of each other. i.e having a flower with a transparent background to be put on grass or dirt on the layer below.I would like to Read From the same file too. How would i go about doing this? Any help would be appreciated. I load the map from a level file which are just numbers corresponding to a tile in the tilesheet. Here is the level file [Layer1] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 [Layer2] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 [Layer3] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 And here is the code that interprets it void LoadMap(const char *filename, std::vector< std::vector <int> > &map) { std::ifstream openfile(filename); if(openfile.is_open()) { std::string line, value; int space; while(!openfile.eof()) { std::getline(openfile, line); if(line.find("[TileSet]") != std::string::npos) { state = TileSet; continue; } else if (line.find("[Layer1]") != std::string::npos) { state = Map; continue; } switch(state) { case TileSet: if(line.length() > 0) tileSet = al_load_bitmap(line.c_str()); break; case Map: std::stringstream str(line); std::vector<int> tempVector; while(!str.eof()) { std::getline(str, value, ' '); if(value.length() > 0) tempVector.push_back(atoi(value.c_str())); } map.push_back(tempVector); break; } } } else { } } and this is how it draws the map. Also the tile sheet is 1280 by 1280 and the tilesizeX and tilesizeY is 64 void DrawMap(std::vector <std::vector <int> > map) { int mapRowCount = map.size(); for(int i, j = 0; i < mapRowCount; i ++) { int mapColCount = map[i].size(); for (int j = 0; j < mapColCount; ++j) { int tilesetIndex = map[i][j]; int tilesetRow = floor(tilesetIndex / TILESET_COLCOUNT); int tilesetCol = tilesetIndex % TILESET_COLCOUNT; al_draw_bitmap_region(tileSet, tilesetCol * TileSizeX, tilesetRow * TileSizeY, TileSizeX, TileSizeY, j * TileSizeX, i * TileSizeX, NULL); } } } EDIT: http://i.imgur.com/Ygu0zRE.jpg

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• Collision 2D Quads

  - by Vico Pelaez

  I want to detect collision between two 2D squares, one square is static and the other one moves according to keyboard arrows. I have implemented some code, however nothing happens when they overlap each other and what I tried to achieve in the code was to detect an overlapping between them. I think I am either not understanding the concept really well or that because one of the squares is moving this is not working. Please I would really appreciate your help. Thank you! float x1=0.05 ,Y1=0.05; float x2=0.05 ,Y2=0.05; float posX1 =0.5, posY1 = 0.5; float movX2 = 0.0 , movY2 = 0.0; struct box{ int width=0.1; int heigth=0.1; }; void init(){ glClearColor(0.0, 0.0, 0.0, 0.0); glColor3f(1.0, 1.0, 1.0); } void quad1(){ glTranslatef(posX1, posY1, 0.0); glBegin(GL_POLYGON); glColor3f(0.5, 1.0, 0.5); glVertex2f(-x1, -Y1); glVertex2f(-x1, Y1); glVertex2f(x1,Y1); glVertex2f(x1,-Y1); glEnd(); } void quad2(){ glMatrixMode(GL_PROJECTION); glLoadIdentity(); glPushMatrix(); glTranslatef(movX2, movY2, 0.0); glBegin(GL_POLYGON); glColor3f(1.5, 1.0, 0.5); glVertex2f(-x2, -Y2); glVertex2f(-x2, Y2); glVertex2f(x2,Y2); glVertex2f(x2,-Y2); glEnd(); glPopMatrix(); } void reset(){ //Reset position of square??? movX2 = 0.0; movY2 = 0.0; collisionB = false; } bool collision(box A, box B){ int leftA, leftB; int rightA, rightB; int topA, topB; int bottomA, bottomB; //Calculate the sides of box A leftA = x1; rightA = x1 + A.width; topA = Y1; bottomA = Y1 + A.heigth; //Calculate the sides of box B leftB = x2; rightB = x2 + B.width; topB = Y1; bottomB = Y1+ B.heigth ; if( bottomA <= topB ) return false; if( topA >= bottomB ) return false; if( rightA <= leftB ) return false; if( leftA >= rightB ) return false; return true; } float move_unit = 0.1; void keyboardown(int key, int x, int y) { switch (key){ case GLUT_KEY_UP: movY2 += move_unit; break; case GLUT_KEY_RIGHT: movX2 += move_unit; break; case GLUT_KEY_LEFT: movX2 -= move_unit; break; case GLUT_KEY_DOWN: movY2 -= move_unit; break; default: break; } glutPostRedisplay(); } void display(){ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_PROJECTION); glLoadIdentity(); cuad1(); if (!collision) { cuad2(); } else{ reset(); } glFlush(); } int main(int argc, char** argv){ glutInit(&argc, argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutInitWindowSize(500,500); glutInitWindowPosition(0, 0); glutCreateWindow("Collision Practice"); glutSpecialFunc(keyboardown); glutDisplayFunc(display); init(); glutMainLoop(); }

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• How to optimize dynamic programming?

  - by Chan

  Problem A number is called lucky if the sum of its digits, as well as the sum of the squares of its digits is a prime number. How many numbers between A and B are lucky? Input: The first line contains the number of test cases T. Each of the next T lines contains two integers, A and B. Output: Output T lines, one for each case containing the required answer for the corresponding case. Constraints: 1 <= T <= 10000 1 <= A <= B <= 10^18 Sample Input: 2 1 20 120 130 Sample Output: 4 1 Explanation: For the first case, the lucky numbers are 11, 12, 14, 16. For the second case, the only lucky number is 120. The problem is quite simple if we use brute force, however the running time is so critical that my program failed most test cases. My current idea is to use dynamic programming by storing the previous sum in a temporary array, so for example: sum_digits(10) = 1 -> sum_digits(11) = sum_digits(10) + 1 The same idea is applied for sum square but with counter equals to odd numbers. Unfortunately, it still failed 9 of 10 test cases which makes me think there must be a better way to solve it. Any idea would be greatly appreciated. #include <iostream> #include <vector> #include <string> #include <algorithm> #include <unordered_map> #include <unordered_set> #include <cmath> #include <cassert> #include <bitset> using namespace std; bool prime_table[1540] = { 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0 }; unsigned num_digits(long long i) { return i > 0 ? (long) log10 ((double) i) + 1 : 1; } void get_sum_and_sum_square_digits(long long n, int& sum, int& sum_square) { sum = 0; sum_square = 0; int digit; while (n) { digit = n % 10; sum += digit; sum_square += digit * digit; n /= 10; } } void init_digits(long long n, long long previous_sum[], const int size = 18) { int current_no_digits = num_digits(n); int digit; for (int i = 0; i < current_no_digits; ++i) { digit = n % 10; previous_sum[i] = digit; n /= 10; } for (int i = current_no_digits; i <= size; ++i) { previous_sum[i] = 0; } } void display_previous(long long previous[]) { for (int i = 0; i < 18; ++i) { cout << previous[i] << ","; } } int count_lucky_number(long long A, long long B) { long long n = A; long long end = B; int sum = 0; int sum_square = 0; int lucky_counter = 0; get_sum_and_sum_square_digits(n, sum, sum_square); long long sum_counter = sum; long long sum_square_counter = sum_square; if (prime_table[sum_counter] && prime_table[sum_square_counter]) { lucky_counter++; } long long previous_sum[19] = {1}; init_digits(n, previous_sum); while (n < end) { n++; if (n % 100000000000000000 == 0) { previous_sum[17]++; sum_counter = previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[16] = 0; previous_sum[15] = 0; previous_sum[14] = 0; previous_sum[13] = 0; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000000000000000 == 0) { previous_sum[16]++; sum_counter = previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[15] = 0; previous_sum[14] = 0; previous_sum[13] = 0; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000000000000000 == 0) { previous_sum[15]++; sum_counter = previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[14] = 0; previous_sum[13] = 0; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100000000000000 == 0) { previous_sum[14]++; sum_counter = previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[13] = 0; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000000000000 == 0) { previous_sum[13]++; sum_counter = previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000000000000 == 0) { previous_sum[12]++; sum_counter = previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100000000000 == 0) { previous_sum[11]++; sum_counter = previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000000000 == 0) { previous_sum[10]++; sum_counter = previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000000000 == 0) { previous_sum[9]++; sum_counter = previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100000000 == 0) { previous_sum[8]++; sum_counter = previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000000 == 0) { previous_sum[7]++; sum_counter = previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000000 == 0) { previous_sum[6]++; sum_counter = previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100000 == 0) { previous_sum[5]++; sum_counter = previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000 == 0) { previous_sum[4]++; sum_counter = previous_sum[4] + previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[4] * previous_sum[4] + previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000 == 0) { previous_sum[3]++; sum_counter = previous_sum[3] + previous_sum[4] + previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[3] * previous_sum[3] + previous_sum[4] * previous_sum[4] + previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100 == 0) { previous_sum[2]++; sum_counter = previous_sum[2] + previous_sum[3] + previous_sum[4] + previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[2] * previous_sum[2] + previous_sum[3] * previous_sum[3] + previous_sum[4] * previous_sum[4] + previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10 == 0) { previous_sum[1]++; sum_counter = previous_sum[1] + previous_sum[2] + previous_sum[3] + previous_sum[4] + previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[1] * previous_sum[1] + previous_sum[2] * previous_sum[2] + previous_sum[3] * previous_sum[3] + previous_sum[4] * previous_sum[4] + previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[0] = 0; } else { sum_counter++; sum_square_counter += ((n - 1) % 10) * 2 + 1; } // get_sum_and_sum_square_digits(n, sum, sum_square); // assert(sum == sum_counter && sum_square == sum_square_counter); if (prime_table[sum_counter] && prime_table[sum_square_counter]) { lucky_counter++; } } return lucky_counter; } void inout_lucky_numbers() { int n; cin >> n; long long a; long long b; while (n--) { cin >> a >> b; cout << count_lucky_number(a, b) << endl; } } int main() { inout_lucky_numbers(); return 0; }

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• Refactoring FizzBuzz

  - by MarkPearl

  A few years ago I blogger about FizzBuzz, at the time the post was prompted by Scott Hanselman who had podcasted about how surprized he was that some programmers could not even solve the FizzBuzz problem within a reasonable period of time during a job interview. At the time I thought I would give the problem a go in F# and sure enough the solution was fairly simple – I then also did a basic solution in C# but never posted it. Since then I have learned that being able to solve a problem and how you solve the problem are two totally different things. Today I decided to give the problem a retry and see if I had learnt anything new in the last year or so. Here is how my solution looked after refactoring… Solution 1 – Cheap and Nasty public class FizzBuzzCalculator { public string NumberFormat(int number) { var numDivisibleBy3 = (number % 3) == 0; var numDivisibleBy5 = (number % 5) == 0; if (numDivisibleBy3 && numDivisibleBy5) return String.Format("{0} FizzBuz", number); else if (numDivisibleBy3) return String.Format("{0} Fizz", number); else if (numDivisibleBy5) return String.Format("{0} Buz", number); return number.ToString(); } } class Program { static void Main(string[] args) { var fizzBuzz = new FizzBuzzCalculator(); for (int i = 0; i < 100; i++) { Console.WriteLine(fizzBuzz.NumberFormat(i)); } } } My first attempt I just looked at solving the problem – it works, and could be an acceptable solution but tonight I thought I would see how far  I could refactor it… The section I decided to focus on was the mass of if..else code in the NumberFormat method. Solution 2 – Replacing If…Else with a Dictionary public class FizzBuzzCalculator { private readonly Dictionary<Tuple<bool, bool>, string> _mappings; public FizzBuzzCalculator(Dictionary<Tuple<bool, bool>, string> mappings) { _mappings = mappings; } public string NumberFormat(int number) { var numDivisibleBy3 = (number % 3) == 0; var numDivisibleBy5 = (number % 5) == 0; var mappedKey = new Tuple<bool, bool>(numDivisibleBy3, numDivisibleBy5); return String.Format("{0} {1}", number, _mappings[mappedKey]); } } class Program { static void Main(string[] args) { var mappings = new Dictionary<Tuple<bool, bool>, string> { { new Tuple<bool, bool>(true, true), "- FizzBuzz"}, { new Tuple<bool, bool>(true, false), "- Fizz"}, { new Tuple<bool, bool>(false, true), "- Buzz"}, { new Tuple<bool, bool>(false, false), ""} }; var fizzBuzz = new FizzBuzzCalculator(mappings); for (int i = 0; i < 100; i++) { Console.WriteLine(fizzBuzz.NumberFormat(i)); } Console.ReadLine(); } } In my second attempt I looked at removing the if else in the NumberFormat method. A dictionary proved to be useful for this – I added a constructor to the class and injected the dictionary mapping. One could argue that this is totally overkill, but if I was going to use this code in a large system an approach like this makes it easy to put this data in a configuration file, which would up its OC (Open for extensibility, closed for modification principle). I could of course take the OC principle even further – the check for divisibility by 3 and 5 is tightly coupled to this class. If I wanted to make it 4 instead of 3, I would need to adjust this class. This introduces my third refactoring. Solution 3 – Introducing Delegates and Injecting them into the class public delegate bool FizzBuzzComparison(int number); public class FizzBuzzCalculator { private readonly Dictionary<Tuple<bool, bool>, string> _mappings; private readonly FizzBuzzComparison _comparison1; private readonly FizzBuzzComparison _comparison2; public FizzBuzzCalculator(Dictionary<Tuple<bool, bool>, string> mappings, FizzBuzzComparison comparison1, FizzBuzzComparison comparison2) { _mappings = mappings; _comparison1 = comparison1; _comparison2 = comparison2; } public string NumberFormat(int number) { var mappedKey = new Tuple<bool, bool>(_comparison1(number), _comparison2(number)); return String.Format("{0} {1}", number, _mappings[mappedKey]); } } class Program { private static bool DivisibleByNum(int number, int divisor) { return number % divisor == 0; } public static bool Divisibleby3(int number) { return number % 3 == 0; } public static bool Divisibleby5(int number) { return number % 5 == 0; } static void Main(string[] args) { var mappings = new Dictionary<Tuple<bool, bool>, string> { { new Tuple<bool, bool>(true, true), "- FizzBuzz"}, { new Tuple<bool, bool>(true, false), "- Fizz"}, { new Tuple<bool, bool>(false, true), "- Buzz"}, { new Tuple<bool, bool>(false, false), ""} }; var fizzBuzz = new FizzBuzzCalculator(mappings, Divisibleby3, Divisibleby5); for (int i = 0; i < 100; i++) { Console.WriteLine(fizzBuzz.NumberFormat(i)); } Console.ReadLine(); } } I have taken this one step further and introduced delegates that are injected into the FizzBuzz Calculator class, from an OC principle perspective it has probably made it more compliant than the previous Solution 2, but there seems to be a lot of noise. Anonymous Delegates increase the readability level, which is what I have done in Solution 4. Solution 4 – Anon Delegates public delegate bool FizzBuzzComparison(int number); public class FizzBuzzCalculator { private readonly Dictionary<Tuple<bool, bool>, string> _mappings; private readonly FizzBuzzComparison _comparison1; private readonly FizzBuzzComparison _comparison2; public FizzBuzzCalculator(Dictionary<Tuple<bool, bool>, string> mappings, FizzBuzzComparison comparison1, FizzBuzzComparison comparison2) { _mappings = mappings; _comparison1 = comparison1; _comparison2 = comparison2; } public string NumberFormat(int number) { var mappedKey = new Tuple<bool, bool>(_comparison1(number), _comparison2(number)); return String.Format("{0} {1}", number, _mappings[mappedKey]); } } class Program { static void Main(string[] args) { var mappings = new Dictionary<Tuple<bool, bool>, string> { { new Tuple<bool, bool>(true, true), "- FizzBuzz"}, { new Tuple<bool, bool>(true, false), "- Fizz"}, { new Tuple<bool, bool>(false, true), "- Buzz"}, { new Tuple<bool, bool>(false, false), ""} }; var fizzBuzz = new FizzBuzzCalculator(mappings, (n) => n % 3 == 0, (n) => n % 5 == 0); for (int i = 0; i < 100; i++) { Console.WriteLine(fizzBuzz.NumberFormat(i)); } Console.ReadLine(); } }   Using the anonymous delegates I think the noise level has now been reduced. This is where I am going to end this post, I have gone through 4 iterations of the code from the initial solution using If..Else to delegates and dictionaries. I think each approach would have it’s pro’s and con’s and depending on the intention of where the code would be used would be a large determining factor. If you can think of an alternative way to do FizzBuzz, add a comment!

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