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Reversing a number in c++

- by Marcel Bujnowski

I created a program to show the sum and show the reversed number a person has typed. The sum function works but the revers function is not. Can anyone give me any tips on how to fix it. I created a program to show the sum and show the reversed number a person has typed. The sum function works but the revers function is not. Can anyone give me any tips on how to fix it. #include<iostream> #include<iomanip> using namespace std; void printSum(int n, bool reverse); int sm(int n); int reverseInt(int n); void printAddTable(int n); int main() { int reverse; int sum=0; int n; cout<<"Enter N value:"<<endl; cin>>n; if(n>0) { reverse = true; printSum( n, reverse); // calls the printSum Method } else { //cout<<"enter positive Number only:"<<endl; } sum = sm(n); //err // calls the sum Method reverse = reverseInt(n); // calls the reverseInt Method cout<<"The reverse value is:"<<reverse; printAddTable(n); // calls the printAddTable Method //getch() } //end of main() void printSum(int n, bool reverse) { int sum=0; // print sum of reverse numbers for(int i=n; i>=1; i--) { sum=sum+i; cout<<i<< " "<<"+"<<" "; } cout<<sum; } int sm(int n) {int sum =0; for(int i=1; i<=n; i++) { sum = sum + i ; cout << endl; cout<<i<<" "<<"+"<<" "<<endl; // print n positive integers cout << endl; } cout<< "Are " <<n<< " positive integers"<<endl; cout<< "Sum is "<<sum <<endl; return sum; } int reverseInt(int n) { int reminder=0; int sum =0; while(n<=0) { reminder = n/10; sum = (sum * 10) + reminder; // it returns the reverse number n = n % 10; } return sum; } void printAddTable(int n) { for(int i=1; i<=n; i++) { cout<<i<<endl; for(int j=1; j<=n; j++) // print n X n add table { cout<<i+j<<endl; } } } {

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SQL SERVER – GUID vs INT – Your Opinion

- by pinaldave

I think the title is clear what I am going to write in your post. This is age old problem and I want to compile the list stating advantages and disadvantages of using GUID and INT as a Primary Key or Clustered Index or Both (the usual case). Let me start a list by suggesting one advantage and one disadvantage in each case. INT Advantage: Numeric values (and specifically integers) are better for performance when used in joins, indexes and conditions. Numeric values are easier to understand for application users if they are displayed. Disadvantage: If your table is large, it is quite possible it will run out of it and after some numeric value there will be no additional identity to use. GUID Advantage: Unique across the server. Disadvantage: String values are not as optimal as integer values for performance when used in joins, indexes and conditions. More storage space is required than INT. Please note that I am looking to create list of all the generic comparisons. There can be special cases where the stated information is incorrect, feel free to comment on the same. Please leave your opinion and advice in comment section. I will combine a final list and update this blog after a week. By listing your name in post, I will also give due credit. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Constraint and Keys, SQL Data Storage, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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DirectX9 / HLSL Shader Model 3 - Passing Doubles between Shaders

- by P. Avery

I need higher precision on a few values within my vertex and pixel shaders...I'm currently using floats, so I would like to use doubles...I've read that HLSL Model 4 has two functions to convert a double into two unsigned integers and back again( asuint() and asdouble() ). These functions are only supported on HLSL 4 and I am using DirectX 9 which will only compile HLSL Model 3 and below... How can I pass a double between shaders? here is implementation for HLSL 4: struct VS_INPUT { float2 v; }; struct PS_INPUT { uint a; uint b; uint c; uint d; }; PS_INPUT VertexShader( VS_INPUT Input ) { PS_INPUT Output = ( PS_INPUT )0; double2 vPos = mul( Input.v, mWorld ).xy; asuint( vPos.x, Output.a, Output.b ); asuint( vPos.y, Output.c, Output.d ); return Output; } float4 PixelShader( PS_INPUT Input ) { double2 vPos; vPos.x = asdouble( Input.a, Input.b ); vPos.y = asdouble( Input.c, Input.d ); ... return 1; }

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Project Euler 14: (Iron)Python

- by Ben Griswold

In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 14. As always, any feedback is welcome. # Euler 14 # http://projecteuler.net/index.php?section=problems&id=14 # The following iterative sequence is defined for the set # of positive integers: # n -> n/2 (n is even) # n -> 3n + 1 (n is odd) # Using the rule above and starting with 13, we generate # the following sequence: # 13 40 20 10 5 16 8 4 2 1 # It can be seen that this sequence (starting at 13 and # finishing at 1) contains 10 terms. Although it has not # been proved yet (Collatz Problem), it is thought that all # starting numbers finish at 1. Which starting number, # under one million, produces the longest chain? # NOTE: Once the chain starts the terms are allowed to go # above one million. import time start = time.time() def collatz_length(n): # 0 and 1 return self as length if n <= 1: return n length = 1 while (n != 1): if (n % 2 == 0): n /= 2 else: n = 3*n + 1 length += 1 return length starting_number, longest_chain = 1, 0 for x in xrange(1, 1000001): l = collatz_length(x) if l > longest_chain: starting_number, longest_chain = x, l print starting_number print longest_chain # Slow 31 seconds print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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Correct For Loop Design

- by Yttrill

What is the correct design for a for loop? Felix currently uses if len a > 0 do for var i in 0 upto len a - 1 do println a.[i]; done done which is inclusive of the upper bound. This is necessary to support the full range of values of a typical integer type. However the for loop shown does not support zero length arrays, hence the special test, nor will the subtraction of 1 work convincingly if the length of the array is equal to the number of integers. (I say convincingly because it may be that 0 - 1 = maxval: this is true in C for unsigned int, but are you sure it is true for unsigned char without thinking carefully about integral promotions?) The actual implementation of the for loop by my compiler does correctly handle 0 but this requires two tests to implement the loop: continue: if not (i <= bound) goto break body if i == bound goto break ++i goto continue break: Throw in the hand coded zero check in the array example and three tests are needed. If the loop were exclusive it would handle zero properly, avoiding the special test, but there'd be no way to express the upper bound of an array with maximum size. Note the C way of doing this: for(i=0; predicate(i); increment(i)) has the same problem. The predicate is tested after the increment, but the terminating increment is not universally valid! There is a general argument that a simple exclusive loop is enough: promote the index to a large type to prevent overflow, and assume no one will ever loop to the maximum value of this type.. but I'm not entirely convinced: if you promoted to C's size_t and looped from the second largest value to the largest you'd get an infinite loop!

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Are C++ templates just a kind of glorified macros?

- by Gulshan

From different comparisons among C++ templates and C#/Java generics like this one- http://stackoverflow.com/questions/31693/what-are-the-differences-between-generics-in-c-and-java-and-templates-in-c/31929#31929 I have a got a perception that, C++ templates are implemented by some kind of preprocessing, not compiling. In other words, they are just a kind of C macros. Is this right? Then I felt that, if C++ templates are implemented by preprocessing, dynamic linking(.dll) cannot be used. A quick google search also supports this. And lastly, how can we use macros in C to deliver C++ templates like functionalities? Another thing came in my mind about templates similar to some kind of preprocessor that, there can be integers passed as arguments to some templates. And it even supports kind of recursion. But the recursion is not in the assembly/machine code. So, am I wrong calling templates glorified macros? Unlike normal macros, it has some superior abilities. But isn't it a kind of preprocessing?

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Enabling XML-documentation for code contracts

- by DigiMortal

One nice feature that code contracts offer is updating of code documentation. If you are using source code documenting features of Visual Studio then code contracts may automate some tasks you otherwise have to implement manually. In this posting I will show you some XML documentation files with documented contracts. I will also explain how this feature works. Enabling XML-documentation in project settings As a first thing let’s enable generating of code documentation under project settings. Open project properties, move to Build page and make check to checkbox called “XML documentation file”. Save project settings and rebuild project. When project is built go to bin/Debug folder and open the XML-file. Here is my XML. <?xml version="1.0"?> <doc> <assembly> <name>Eneta.Examples.CodeContracts.Testable</name> </assembly> <members> <member name="T:Eneta.Examples.CodeContracts.Testable.Randomizer"> <summary> Class for generating random integers in user specified range. </summary> </member> <member name="M:Eneta.Examples.CodeContracts.Testable.Randomizer.#ctor(Eneta.Examples.CodeContracts.Testable.IRandomGenerator)"> <summary> Constructor of Randomizer. Initializes Randomizer class. </summary> <param name="generator">Instance of random number generator.</param> </member> <member name="M:Eneta.Examples.CodeContracts.Testable.Randomizer.GetRandomFromRangeContracted(System.Int32,System.Int32)"> <summary> Returns random integer in given range. </summary> <param name="min">Minimum value of random integer.</param> <param name="max">Maximum value of random integer.</param> </member> </members> </doc> You can see nothing about code contracts here. Enabling code contracts documentation Code contracts have their own settings and conditions for documentation. Open project properties and move to Code Contracts tab. From “Contract Reference Assembly” dropdown check Build and make check to checkbox “Emit contracts into XML doc file”. And again – save project setting, build the project and move to bin/Debug folder. Now you can see that there are two files for XML-documentation: <assembly name>.XML <assembly name>.old.XML First files is documentation with contracts, second file is original documentation without contracts. Let’s see now what is inside our new XML-documentation file. <?xml version="1.0"?> <doc> <assembly> <name>Eneta.Examples.CodeContracts.Testable</name> </assembly> <members> <member name="T:Eneta.Examples.CodeContracts.Testable.Randomizer"> <summary> Class for generating random integers in user specified range. </summary> </member> <member name="M:Eneta.Examples.CodeContracts.Testable.Randomizer.#ctor(Eneta.Examples.CodeContracts.Testable.IRandomGenerator)"> <summary> Constructor of Randomizer. Initializes Randomizer class. </summary> <param name="generator">Instance of random number generator.</param> </member> <member name="M:Eneta.Examples.CodeContracts.Testable.Randomizer.GetRandomFromRangeContracted(System.Int32,System.Int32)"> <summary> Returns random integer in given range. </summary> <param name="min">Minimum value of random integer.</param> <param name="max">Maximum value of random integer.</param> <requires description="Min must be less than max" exception="T:System.ArgumentOutOfRangeException"> min < max</requires> <exception cref="T:System.ArgumentOutOfRangeException"> min >= max</exception> <ensures description="Return value is out of range"> Contract.Result<int>() >= min && Contract.Result<int>() <= max</ensures> </member> </members> </doc> As you can see then code contracts are pretty well documented. Messages that I provided with code contracts are also available in documentation. If I wrote very good and informative messages then these messages are very useful also in contracts documentation. Code contracts and Sandcastle Sandcastle knows nothing about code contracts by default. There is separate package of file for Sandcastle that is provided you by code contracts installation. You can read from code contracts manual: “Sandcastle (http://www.codeplex.com/Sandcastle) is a freely available tool that generates help les and web sites describing your APIs, based on the XML doc comments in your source code. The CodeContracts install contains a set of les that can be copied over a Sandcastle installation to take advantage of the additional contract information. The produced documentation adds a contract section to methods with declared requires and/or ensures. In order for Sandcastle to produce Contract sections, you need to patch a number of files in its installation. Please refer to the Sandcastle Readme.txt found under Start Menu/CodeContracts/Sandcastle for instructions. A future release of Sandcastle will hopefully support contract sections without the need for this patching step.” Integrating code contracts documentation to Sandcastle will be one of my next postings about code contracts. Conclusion if you are using code documentation then documentation about code contracts can be added to documentation very easily. All you have to do is to enable XML-documentation for contracts and build your project. Later you can use Sandcastle files provided by code contracts installer to integrate contracts documentation to your output documentation package.

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How to make game sessions like "with friends" games?

- by Miguel lugo

I want to make a game like "words with friends" or "chess with friends" or "Draw Something" or any of the other online multiplayer type games that are based around friends having game sessions with each other. I have made one app before that had no online features so I know the basics of objective-C and xCode. I looked up facebook connect so I know how to make friends find other friends to play with through Facebook. Just not how to make the gaming session. I only need my game to send a small array (or XML if it's better) of strings and integers from one iPhone to the other as each iPhone takes a turn. I'm NOT sending some complex video or anything like in "Draw Something." I was hoping someone could point me in the right direction (whether link to website or book or just a general idea) for how to do gaming sessions between two iPhones. I read this tutorial http://www.raywenderlich.com/3932/how-to-create-a-socket-based-iphone-app-and-server but it seems to be more about having two iPhones communicate over a server on a laptop or through the same wifi, not how to have iPhones game together over any Internet connection like in "with friends" games. I've tried to research this in other places but I'm never quite sure if what the articles I find are talking about is related to what I want or not. Someone please just point me in the right direction or give me a general outline of what to do. I will look up the specifics on my own once I know what to look for. Thank you.

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Greiner-Hormann clipping problem

- by Belgin

I have a set of planar polygons in 3D space defined by their vertices in counterclockwise order. Let's define the 'positive face' as being the face of the 3D polygon such as when observed, the vertices appear in counterclockwise order, and the 'negative face', the face which when observed, the vertices appear in clockwise order. I'm doing perspective projection of the set of polygons onto a projection polygon defined by the points in this order: (0, h, 0), (0, 0, 0), (w, 0, 0), and (w, h, 0), where w and h are strictly positive integers. The positive face of this projection polygon is oriented towards positive Z, and the camera point is somewhere at (0, 0, d), where d is a strictly negative number. In order to 'clip' the projected polygons into the projection polygon, I'm applying the Greiner-Hormann (PDF) clipping algorithm, which requires that the clipper and the to-be-clipped polygons be in the same order (i.e. clockwise or counterclockwise). My question is the following: How can I determine whether the projected face of the 3D polygon is the negative or the positive one? Meaning, how do I find out if I have to work with the vertices in normal or inverted order for the algorithm to work? I noticed that only if the 3D polygon is facing the projection polygon with its negative face, both of them are in the same order (counterclockwise), otherwise, a modification needs to be done. Here is a picture (PNG) that illustrates this. Note that the planes described by the polygon from the set and the projection polygon may not always be parallel.

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Game Trees Conceptual Question

- by Chris Corbin

I am struggling to conceptually understand a question in a programming assignment for an algorithms class. The problem is dealing with a fictitious 2 player game, named Easy. The rules of the game are simple; each player may chose one of 4 integers {0-3} after which that integer is not available for the other player. The catch is, a player picks {0} it means they quit. The objective is for Player 1 to get {1} and Player 2 to get {2}, in which case they may win, however if both or neither succeed, then the game ends in a draw. I have been asked to draw the game tree for Easy, showing all nodes, which they explained as 4! = 24. Labeling the edges, which represent moves (selecting a number) and the leaves with who won (1 means Player 1 won, -1 means Player 2 won, and 0 means a tie). I have drawn out a game tree, which I believe is correct, however I am not 100% certain hence I am asking the question. My game tree only has 16 leaves. I am thinking that when a player picks {0}, and then quits, the game tree stops there? I don't see how it is possible to get to 24 leaves? Any help would be greatly appreciate, and if you need more information I would be happy to provide it. Thanks

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How to define type-specific scripts when using a 'type object' programming pattern?

- by Erik

I am in the process of creating a game engine written in C++, using the C/C++ SQLite interface to achieve a 'type object' pattern. The process is largely similar to what is outlined here (Thank you Bob Nystrom for the great resource!). I have a generally defined Entity class that when a new object is created, data is taken from a SQLite database and then is pushed back into a pointer vector, which is then iterated through, calling update() for each object. All the ints, floats, strings are loaded in fine, but the script() member of Entity is proving an issue. It's not much fun having a bunch of stationary objects laying around my gameworld. The only solutions I've come up with so far are: Create a monolithic EntityScript class with member functions encompassing all game AI and then calling the corresponding script when iterating through the Entity vector. (Not ideal) Create bindings between C++ and a scripting language. This would seem to get the job done, but it feels like implementing this (given the potential memory overhead) and learning a new language is overkill for a small team (2-3 people) that know the entirety of the existing game engine. Can you suggest any possible alternatives? My ideal situation would be that to add content to the game, one would simply add a script file to the appropriate directory and append the SQLite database with all the object data. All that is required is to have a variety of integers and floats passed between both the engine and the script file.

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What is a technique for 2D ray-box intersection that is suitable for old console hardware?

- by DJCouchyCouch

I'm working on a Sega Genesis homebrew game (it has a 7mhz 68000 CPU). I'm looking for a way to find the intersection between a particle sprite and a background tile. Particles are represented as a point with a movement vector. Background tiles are 8 x 8 pixels, with an (X,Y) position that is always located at a multiple of 8. So, really, I need to find the intersection point for a ray-box collision; I need to find out where along the edge of the tile the ray/particle hits. I have these two hard constraints: I'm working with pixel locations (integers). Floating point is too expensive. It doesn't have to be super exact, just close enough. Multiplications, divisions, dot products, et cetera, are incredibly expensive and are to be avoided. So I'm looking for an efficient algorithm that would fit those constraints. Any ideas? I'm writing it in C, so that would work, but assembly should be good as well.

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Multi-Resolution Mobile Development

- by user2186302

I'm about to start development on my first game for mobile phone (I already have a flash prototype completed so it's jsut a matter of "porting" it to mobile and fixing up the code) and plan on hopefully being able to get the game working on iphones and most android devices. I am using Haxe along with OpenFL and HaxeFlixel for development. My question is: What resolution should I design the game in initially and/or what is the best way to develop a game for multiple resolutions. I have found multiple different methods, the best, in my opinion, being strategy 3 on this page: http://wiki.starling-framework.org/manual/multi-resolution_development. However I have some questions about this. First, what would the best base resolution to use be, the guide suggests 240*320 which seems alright to me, although if I chose to use pixel graphics as I most probably will given I'm using HaxeFlixel, I'm not sure if they'll look too blocky on larger screens which I'm not even sure is a problem as it might still look alright. (Honestly, not sure about that and if anyone has any examples of games that use this method and look nice). Finally, please feel free to share whatever methods you use and think is best. For example, HaxeFlixel has a scaling feature that scales the game to fit the exact screen size, but I'm afraid that would lead to blurry and improperly scaled graphics since it would scale by non-integers. But, I'm not sure how noticeable a problem that may or may not be. Although from experience I'm pretty sure it won't look nice and currently I do not think I'm going to go for this option. So, I would really appreciate any help on this subject. Thank you in advance.

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Precision loss when transforming from cartesian to isometric

- by Justin Skiles

My goal is to display a tile map in isometric projection. This tile map has 25 tiles across and 25 tiles down. Each tile is 32x32. See below for how I'm accomplishing this. World Space World Space to Screen Space Rotation (45 degrees) Using a 2D rotation matrix, I use the following: double rotation = Math.PI / 4; double rotatedX = ((tileWorldX * Math.Cos(rotation)) - ((tileWorldY * Math.Sin(rotation))); double rotatedY = ((tileWorldX * Math.Sin(rotation)) + (tileWorldY * Math.Cos(rotation))); World Space to Screen Space Scale (Y-axis reduced by 50%) Here I simply scale down the Y value by a factor of 0.5. Problem And it works, kind of. There are some tiny 1px-2px gaps between some of the tiles when rendering. I think there's some precision loss somewhere, or I'm not understanding how to get these tiles to fit together perfectly. I'm not truncating or converting my values to non-decimal types until I absolutely have to (when I pass to the render method, which only takes integers). I'm not sure how to guarantee pixel perfect rendering precision when I'm rotating and scaling on a level of higher precision. Any advice? Do I need to supply for information?

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2D Side scroller collision detection

- by Shanon Simmonds

I am trying to do some collision detection between objects and tiles, but the tiles do not have there own x and y position, they are just rendered to the x and y position given, there is an array of integers which has the ids of the tiles to use(which are given from an image and all the different colors are assigned different tiles) int x0 = camera.x / 16; int y0 = camera.y / 16; int x1 = (camera.x + screen.width) / 16; int y1 = (camera.y + screen.height) / 16; for(int y = y0; y < y1; y++) { if(y < 0 || y >= height) continue; // height is the height of the level for(int x = x0; x < x1; x++) { if(x < 0 || x >= width) continue; // width is the width of the level getTile(x, y).render(screen, x * 16, y * 16); } } I tried using the levels getTile method to see if the tile that the object was going to advance to, to see if it was a certain tile, but, it seems to only work in some directions. Any ideas on what I'm doing wrong and fixes would be greatly appreciated. What's wrong is that it doesn't collide properly in every direction and also this is how I tested for a collision in the objects class if(!level.getTile((x + xa) / 16, (y + ya) / 16).isSolid()) { x += xa; y += ya; } EDIT: xa and ya represent the direction as well as the movement, if xa is negative it means the object is moving left, if its positive it is moving right, and same with ya except negative for up, positive for down.

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Why isn't there a typeclass for functions?

- by Steve314

I already tried this on Reddit, but there's no sign of a response - maybe it's the wrong place, maybe I'm too impatient. Anyway... In a learning problem I've been messing around with, I realised I needed a typeclass for functions with operations for applying, composing etc. Reasons... It can be convenient to treat a representation of a function as if it were the function itself, so that applying the function implicitly uses an interpreter, and composing functions derives a new description. Once you have a typeclass for functions, you can have derived typeclasses for special kinds of functions - in my case, I want invertible functions. For example, functions that apply integer offsets could be represented by an ADT containing an integer. Applying those functions just means adding the integer. Composition is implemented by adding the wrapped integers. The inverse function has the integer negated. The identity function wraps zero. The constant function cannot be provided because there's no suitable representation for it. Of course it doesn't need to spell things as if it the values were genuine Haskell functions, but once I had the idea, I thought a library like that must already exist and maybe even using the standard spellings. But I can't find such a typeclass in the Haskell library. I found the Data.Function module, but there's no typeclass - just some common functions that are also available from the Prelude. So - why isn't there a typeclass for functions? Is it "just because there isn't" or "because it's not so useful as you think"? Or maybe there's a fundamental problem with the idea? The biggest possible problem I've thought of so far is that function application on actual functions would probably have to be special-cased by the compiler to avoid a looping problem - in order to apply this function I need to apply the function application function, and to do that I need to call the function application function, and to do that...

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Name of the Countdown Numbers round problem - and algorithmic solutions?

- by Dai

For the non-Brits in the audience, there's a segment of a daytime game-show where contestants have a set of 6 numbers and a randomly generated target number. They have to reach the target number using any (but not necessarily all) of the 6 numbers using only arithmetic operators. All calculations must result in positive integers. An example: Youtube: Countdown - The Most Extraordinary Numbers Game Ever? A detailed description is given on Wikipedia: Countdown (Game Show) For example: The contentant selects 6 numbers - two large (possibilities include 25, 50, 75, 100) and four small (numbers 1 .. 10, each included twice in the pool). The numbers picked are 75, 50, 2, 3, 8, 7 are given with a target number of 812. One attempt is (75 + 50 - 8) * 7 - (3 * 2) = 813 (This scores 7 points for a solution within 5 of the target) An exact answer would be (50 + 8) * 7 * 2 = 812 (This would have scored 10 points exactly matching the target). Obviously this problem has existed before the advent of TV, but the Wikipedia article doesn't give it a name. I've also saw this game at a primary school I attended where the game was called "Crypto" as an inter-class competition - but searching for it now reveals nothing. I took part in it a few times and my dad wrote an Excel spreadsheet that attempted to brute-force the problem, I don't remember how it worked (only that it didn't work, what with Excel's 65535 row limit), but surely there must be an algorithmic solution for the problem. Maybe there's a solution that works the way human cognition does (e.g. in-parallel to find numbers 'close enough', then taking candidates and performing 'smaller' operations).

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Project Euler Problem 14

- by MarkPearl

The Problem The following iterative sequence is defined for the set of positive integers: n n/2 (n is even) n 3n + 1 (n is odd) Using the rule above and starting with 13, we generate the following sequence: 13 40 20 10 5 16 8 4 2 1 It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1. Which starting number, under one million, produces the longest chain? NOTE: Once the chain starts the terms are allowed to go above one million. The Solution public static long NextResultOdd(long n) { return (3 * n) + 1; } public static long NextResultEven(long n) { return n / 2; } public static long TraverseSequence(long n) { long x = n; long count = 1; while (x > 1) { if (x % 2 == 0) x = NextResultEven(x); else x = NextResultOdd(x); count++; } return count; } static void Main(string[] args) { long largest = 0; long pos = 0; for (long i = 1000000; i > 1; i--) { long temp = TraverseSequence(i); if (temp > largest) { largest = temp; pos = i; } } Console.WriteLine("{0} - {1}", pos, largest); Console.ReadLine(); }

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Finding maximum number of congruent numbers

- by Stefan Czarnecki

Let's say we have a multiset (set with possible duplicates) of integers. We would like to find the size of the largest subset of the multiset such that all numbers in the subset are congruent to each other modulo some m 1. For example: 1 4 7 7 8 10 for m = 2 the subsets are: (1, 7, 7) and (4, 8, 10), both having size 3. for m = 3 the subsets are: (1, 4, 7, 7, 10) and (8), the larger set of size 5. for m = 4 the subsets are: (1), (4, 8), (7, 7), (10), the largest set of size 2. At this moment it is evident that the best answer is 5 for m = 3. Given m we can find the size of the largest subset in linear time. Because the answer is always equal or larger than half of the size of the set, it is enough to check for values of m upto median of the set. Also I noticed it is necessary to check for only prime values of m. However if values in the set are large the algorithm is still rather slow. Does anyone have any ideas how to improve it?

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What language available on commodity web hosts would suit a C# developer? [closed]

- by billpg

Recognising its ubiquity on commodity web hosting services, I tried developing in PHP a few years ago. I really didn't like it, later deciding that life was too short for PHP. (In brief, having to put $ on variable names; mis-spelt variable names become new variables; converting non-numeric strings to integers without complaint; the need for an "and this time I mean it" comparison operator.) In my ideal world, commodity web hosts would all support C#/ASP.NET, my preferred web-development language and framework, but this is not my ideal world. Even Mono has barely made a dent on Linux based hosts. However, last time I moaned about PHP's ubiquity, someone followed up that this was no longer the case, and that many other languages are now commonly usable on web hosts too. What programming language; a. Would suit a developer who prefers C#. b. Is available to run on many web hosts.

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LINQ – Skip() and Take() methods

- by nmarun

I had this issue recently where I have an array of integers and I’m doing some Skip(n) and then a Take(m) on the collection. Here’s an abstraction of the code: 1: int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 2: var taken = numbers.Skip(3).Take(3); 3: foreach (var i in taken) 4: { 5: Console.WriteLine(i); 6: } The output is as expected: 3, 9, 8 – skip the first three and then take the next three items. But, what happens if I do something like: 1: var taken = numbers.Skip(7).Take(5); In English – skip the first seven and the take the next 5 items from an array that contains only 10 elements. Think it’ll throw the IndexOutOfRangeException exception? Nope. These extension methods are a little smarter than that. Even though the user has requested more elements than what exists in the collection, the Take method only returns the first three thereby making the output of the program as: 7, 2, 0. The scenario is handled similarly when you do: 1: var taken = numbers.Take(5).Skip(7); This one takes the first 5 elements from the numbers array and then skips 7 of them. This is what is looks like in the debug mode: Just wanted to share this behavior.

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Create a rectangle struct to be rotated and have a .Intersects() function

- by MintyAnt

In my XNA program, I am trying to swing a sword. The sword starts at an angle of 180 degrees, then rotates (clockwise) to an angle of 90 degrees. The Rectangle struct that XNA provides, Rectangle mAttackBox = new Rectangle(int x, int y, int width, int height); However, this struct has two problems: Holds position and size in Integers, not Floats Cannot be rotated I was hoping someone could help me in either telling me that i'm wrong and the Rectangle can be used for both these methods, or can lead me down the right path for rotating a rectangle. I know how to create a Struct. I believe that I can make methods like classes. I can determine the 4 vertices of a 2D rectangle by calculating out the x,y of the other 3 given the length, width. I'm sure theres a Matrix class I can use to multiply each point against a Rotation matrix. But once i have my 4 vertices, I got two other problems: - How do I test other rectangles against it? How does .Intersects() work for the rectangle struct? - Is this even the fastest way to do it? I'd be constantly doing matrix multiplication, wouldnt that slow things down?

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Java Program Compilaton on Windows [closed]

- by Mc Elroy

I am trying to compile my program on the command line on windows using the java command and it says: Error: could not find or load main class or addition class It is for a program for adding two integers. I don't understand how to resolve the problem since I defined the static main class in my source code here is it: //Filename:addition.java //Usage: this program adds two numbers and displays their sum. //Author: Nyah Check, Developer @ Ink Corp.. //Licence: No warranty following the GNU Public licence import java.util.Scanner; //this imports the scanner class. public class addition { public static void main(String[] args) { Scanner input = new Scanner(System.in);//this creates scanners instance to take input from the input. int input1, input2, sum; System.out.printf("\nEnter First Integer: "); input1 = input.nextInt(); System.out.printf("\nEnter Second Integer: "); input2 = input.nextInt(); sum = input1 + input2; System.out.printf("\nThe Sum is: %d", sum); } }//This ends the class definition

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Value my C++ knowledge

- by PirateOwh

I have only followed antiRTFM tutorials and read 2 books So, I'll list the things I know better : basic input output and all the variables : integers ( signed unsigned ), float, double, char arrays if, for, while, switch functions, and passing variables to functions and return type thing classes and the concept of oop with separating declaration and definition in the header and in the source pointers so this and some more i think is all i know of C++.. But, i need some exercises to test my knowledge because i want to move on to the library SDL, so I don't know if i should feel ready or not to move on to something totally different.. I feel I should know the basics for good at least. So the question is : How can i value my c++ knowledge? Is there any online tests? Is there any GDD ( Game Design Document ) for free to use and see if i can manage to do it so "i'd pass" ? ( I'm saying GDD since ill move on to SDL and try to make my own game ) When should I move to SDL? What are ALL the things I should "master" ( master is a big word to say.. but so you understand what i mean ) before moving on ? Please I'm really in need of expert advice. I think my question is detailed so i hope you understand what i mean and can give me a good reply. Thanks for the help!

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Please help me debug this little C program on dynamic two-dimensional array? [migrated]

- by azhi

I am a newbie here. I have written a little C program, which is to create a two-dimensional matrix. Here is the code: #include <stdio.h> #include <stdlib.h> int **CreatMatrix(int m,int n){ int **Matrix; int i; Matrix=(int**)malloc(m*sizeof(int*)); for(i=0;i<m;i++){ Matrix[i]=(int*)malloc(n*sizeof(int)); } return Matrix; } int main(){ int m,n; int **A; printf("Please input the size of the Matrix: "); scanf("%d%d",&m,&n); A=CreatMatrix(m,n); printf("Please input the entries of the Matrix, which should be integers!\n"); int i,j; for(i=0;i<m;i++){ for(j=0;j<n;j++){ scanf("%d",&A[i][j]); } } printf("The Matrix that you input is:\n"); for(i=0;i<m;i++){ for(j=0;j<n;j++){ printf("%3d ",A[i][j]); } printf("\n"); } for(i=0;i<m;i++) free(A[i]); free(A); } I have run it, and it works fine. But I am not sure if it is right? Can anyone help me debug it?

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