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  • C++ priority queue structure userd ?

    - by John Retallack
    While searching for some functions in C++ STL documentation I read that push and pop for priority queues needs constant time. "Constant (in the priority_queue). Although notice that push_heap operates in logarithmic time." My question is what kind of data structure is used to mantain a priority queue with O(1) for push and pop ?

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  • Determine coordinates of rotated rectangle

    - by MathieuK
    I'm creating an utility application that should detect and report the coordinates of the corners of a transparent rectangle (alpha=0) within an image. So far, I've set up a system with Javascript + Canvas that displays the image and starts a floodfill-like operation when I click inside the transparent rectangle in the image. It correctly determines the bounding box of the floodfill operation and as such can provide me the correct coordinates. Here's my implementation so-far: http://www.scriptorama.nl/image/ (works in recent Firefox / Safari ). However, the bounding box approach breaks down then the transparent rectangle is rotated (CW or CCW) as the resulting bounding box no longer properly represents the proper width and height. I've tried to come up with a few alternatives to detect to corners, but have not been able to think up a proper solution. So, does anyone have any suggestions on how I might approach this so I can properly detect the coordinates of 4 corners of the rotated rectangle?

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  • help implementing All Nearest Smaller Values algorithm

    - by davit-datuashvili
    http://en.wikipedia.org/wiki/All_nearest_smaller_values this is site of the problem and here is my code but i have some trouble to implement it import java.util.*; public class stack{ public static void main(String[]args){ int x[]=new int[]{ 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15 }; Stack<Integer> st=new Stack<Integer>(); for (int a:x){ while (!st.empty() && st.pop()>=a){ System.out.println( st.pop()); if (st.empty()){ break; } else{ st.push(a); } } } } } and here is pseudo code from site S = new empty stack data structure for x in the input sequence: while S is nonempty and the top element of S is greater than or equal to x: pop S if S is empty: x has no preceding smaller value else: the nearest smaller value to x is the top element of S push x onto S

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  • What is the best way to find the digit at n position in a decimal number?

    - by Elijah
    Background I'm working on a symmetric rounding class and I find that I'm stuck with regards to how to best find the number at position x that I will be rounding. I'm sure there is an efficient mathematical way to find the single digit and return it without having to resort to string parsing. Problem Suppose, I have the following (C#) psuedo-code: var position = 3; var value = 102.43587m; // I want this no ? (that is 5) protected static int FindNDigit(decimal value, int position) { // This snippet is what I am searching for } Also, it is worth noting that if my value is a whole number, I will need to return a zero for the result of FindNDigit. Does anyone have any hints on how I should approach this problem? Is this something that is blaringly obvious that I'm missing?

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  • Elegant Method of Inserting Code Between Loops

    - by DeathMagus
    In web development, I often find I need to format and print various arrays of data, and separate these blocks of data in some manner. In other words, I need to be able to insert code between each loop, without said code being inserted before the first entry or after the last one. The most elegant way I've found to accomplish this is as follows: function echoWithBreaks($array){ for($i=0; $i<count($array); $i++){ //Echo an item if($i<count($array)-1){ //Echo "between code" } } } Unfortunately, there's no way that I can see to implement this solution with foreach instead of for. Does anyone know of a more elegant solution that will work with foreach?

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  • Dynamic Programming resources in C?

    - by EsotericMe
    Hi everyone, I'll be writing the online Google test tomorrow as a fresher. Apparently, they definitely ask one problem on Dynamic Programming? Does anyone know of a good resource for collection of DP problems in C along with solutions? I know what DP is & have used it on an occasion or twice. However I feel to crack a DP problem in test, prior practice of typical problems will make it easier to approach. Any good resources or problem sets with solutions in C will be highly appreciated. Thanks.

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  • Linked list Recursion ...

    - by epsilon_G
    hey , I'd like to make a recursive function using C++ I make this class class linklist { private: struct node { int data; node *link; }*p; void linklist::print_num(node* p) { if (p != NULL) { cout << p->data << " "; print_num (p->link); } } in the main program what should I write ...

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  • Setting last N bits in an array

    - by Martin
    I'm sure this is fairly simple, however I have a major mental block on it, so I need a little help here! I have an array of 5 integers, the array is already filled with some data. I want to set the last N bits of the array to be random noise. [int][int][int][int][int] set last 40 bits [unchanged][unchanged][unchanged][24 bits of old data followed 8 bits of randomness][all random] This is largely language agnostic, but I'm working in C# so bonus points for answers in C#

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  • Optimizing a Parking Lot Problem. What algorithims should I use to fit the most amount of cars in th

    - by Adam Gent
    What algorithms (brute force or not) would I use to put in as many cars (assume all cars are the same size) in a parking lot so that there is at least one exit (from the container) and a car cannot be blocked. Or can someone show me an example of this problem solved programmatically. The parking lot varies in shape would be nice but if you want to assume its some invariant shape that is fine. Another Edit: Assume that driving distance in the parking lot is not a factor (although it would be totally awesome if it was weighted factor to number of cars in lot). Another Edit: Assume 2 Dimensional (no cranes or driving over cars). Another Edit: You cannot move cars around once they are parked (its not a valet parking lot). I hope the question is specific enough now.

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  • Is this linear search implementation actually useful?

    - by Helper Method
    In Matters Computational I found this interesting linear search implementation (it's actually my Java implementation ;-)): public static int linearSearch(int[] a, int key) { int high = a.length - 1; int tmp = a[high]; // put a sentinel at the end of the array a[high] = key; int i = 0; while (a[i] != key) { i++; } // restore original value a[high] = tmp; if (i == high && key != tmp) { return NOT_CONTAINED; } return i; } It basically uses a sentinel, which is the searched for value, so that you always find the value and don't have to check for array boundaries. The last element is stored in a temp variable, and then the sentinel is placed at the last position. When the value is found (remember, it is always found due to the sentinel), the original element is restored and the index is checked if it represents the last index and is unequal to the searched for value. If that's the case, -1 (NOT_CONTAINED) is returned, otherwise the index. While I found this implementation really clever, I wonder if it is actually useful. For small arrays, it seems to be always slower, and for large arrays it only seems to be faster when the value is not found. Any ideas?

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  • How to perform a Depth First Search iteratively using async/parallel processing?

    - by Prabhu
    Here is a method that does a DFS search and returns a list of all items given a top level item id. How could I modify this to take advantage of parallel processing? Currently, the call to get the sub items is made one by one for each item in the stack. It would be nice if I could get the sub items for multiple items in the stack at the same time, and populate my return list faster. How could I do this (either using async/await or TPL, or anything else) in a thread safe manner? private async Task<IList<Item>> GetItemsAsync(string topItemId) { var items = new List<Item>(); var topItem = await GetItemAsync(topItemId); Stack<Item> stack = new Stack<Item>(); stack.Push(topItem); while (stack.Count > 0) { var item = stack.Pop(); items.Add(item); var subItems = await GetSubItemsAsync(item.SubId); foreach (var subItem in subItems) { stack.Push(subItem); } } return items; } EDIT: I was thinking of something along these lines, but it's not coming together: var tasks = stack.Select(async item => { items.Add(item); var subItems = await GetSubItemsAsync(item.SubId); foreach (var subItem in subItems) { stack.Push(subItem); } }).ToList(); if (tasks.Any()) await Task.WhenAll(tasks); UPDATE: If I wanted to chunk the tasks, would something like this work? foreach (var batch in items.BatchesOf(100)) { var tasks = batch.Select(async item => { await DoSomething(item); }).ToList(); if (tasks.Any()) { await Task.WhenAll(tasks); } } The language I'm using is C#.

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  • generic binary Search in c#

    - by Pro_Zeck
    Below is my Generic Binary Search it works ok with the intgers type array it finds all the elements in it . But the Problem Arises when i use a string array to find any string data. It runs ok for the first index and last index elements but i cant find the middle elements. Stringarray = new string[] { "b", "a", "ab", "abc", "c" }; public static void BinarySearch<T>(T[] array, T searchFor, Comparer<T> comparer) { int high, low, mid; high = array.Length - 1; low = 0; if (array[0].Equals(searchFor)) Console.WriteLine("Value {0} Found At Index {1}",array[0],0); else if (array[high].Equals(searchFor)) Console.WriteLine("Value {0} Found At Index {1}", array[high], high); else { while (low <= high) { mid = (high + low) / 2; if (comparer.Compare(array[mid], searchFor) == 0) { Console.WriteLine("Value {0} Found At Index {1}", array[mid], mid); break; } else { if (comparer.Compare(searchFor, array[mid]) > 0) high = mid + 1; else low = mid + 1; } } if (low > high) { Console.WriteLine("Value Not Found In the Collection"); } } }

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  • How do I recursively define a Hash in Ruby from supplied arguments?

    - by Sarah Beckham
    This snippet of code populates an @options hash. values is an Array which contains zero or more heterogeneous items. If you invoke populate with arguments that are Hash entries, it uses the value you specify for each entry to assume a default value. def populate(*args) args.each do |a| values = nil if (a.kind_of? Hash) # Converts {:k => "v"} to `a = :k, values = "v"` a, values = a.to_a.first end @options[:"#{a}"] ||= values ||= {} end end What I'd like to do is change populate such that it recursively populates @options. There is a special case: if the values it's about to populate a key with are an Array consisting entirely of (1) Symbols or (2) Hashes whose keys are Symbols (or some combination of the two), then they should be treated as subkeys rather than the values associated with that key, and the same logic used to evaluate the original populate arguments should be recursively re-applied. That was a little hard to put into words, so I've written some test cases. Here are some test cases and the expected value of @options afterwards: populate :a => @options is {:a => {}} populate :a => 42 => @options is {:a => 42} populate :a, :b, :c => @options is {:a => {}, :b => {}, :c => {}} populate :a, :b => "apples", :c => @options is {:a => {}, :b => "apples", :c => {}} populate :a => :b => @options is {:a => :b} # Because [:b] is an Array consisting entirely of Symbols or # Hashes whose keys are Symbols, we assume that :b is a subkey # of @options[:a], rather than the value for @options[:a]. populate :a => [:b] => @options is {:a => {:b => {}}} populate :a => [:b, :c => :d] => @options is {:a => {:b => {}, :c => :d}} populate :a => [:a, :b, :c] => @options is {:a => {:a => {}, :b => {}, :c => {}}} populate :a => [:a, :b, "c"] => @options is {:a => [:a, :b, "c"]} populate :a => [:one], :b => [:two, :three => "four"] => @options is {:a => :one, :b => {:two => {}, :three => "four"}} populate :a => [:one], :b => [:two => {:four => :five}, :three => "four"] => @options is {:a => :one, :b => { :two => { :four => :five } }, :three => "four" } } It is acceptable if the signature of populate needs to change to accommodate some kind of recursive version. There is no limit to the amount of nesting that could theoretically happen. Any thoughts on how I might pull this off?

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  • Given a number N, find the number of ways to write it as a sum of two or more consecutive integers

    - by hilal
    Here is the problem (Given a number N, find the number of ways to write it as a sum of two or more consecutive integers) and example 15 = 7+8, 1+2+3+4+5, 4+5+6 I solved with math like that : a + (a + 1) + (a + 2) + (a + 3) + ... + (a + k) = N (k + 1)*a + (1 + 2 + 3 + ... + k) = N (k + 1)a + k(k+1)/2 = N (k + 1)*(2*a + k)/2 = N Then check that if N divisible by (k+1) and (2*a+k) then I can find answer in O(N) time Here is my question how can you solve this by dynamic-programming ? and what is the complexity (O) ? P.S : excuse me, if it is a duplicate question. I searched but I can find

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  • Find recipes that can be cooked from provided ingridients

    - by skaurus
    Sorry for bad English :( Suppose i can preliminary organize recipes and ingredients data in any way. How can i effectively conduct search of recipes by user-provided ingredients, preferably sorted by max match - so, first going recipes that use maximum of provided ingridients and do not contain any other ingrs, after them recipes that uses less of provided set and still not any other ingrs, after them recipes with minimum additional requirements and so on? All i can think about is represent recipe ingridients like bitmasks, and compare required bitmask with all recipes, but it is obviously a bad way to go. And related things like Levenstein distance i don't see how to use here. I believe it should be quite common task...

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  • Effective way to calculate a similarity percentage between data sets

    - by UltraVi01
    I am currently working with User objects -- each of which have many Goal objects. The Goal objects are not User specific, that is, Users can share the same Goal. I am attempting to fashion a way to calculate a "similarity percentage" between two Users... (i.e., taking into account how many Goals they share as well as how many Goals they do not share) Does anyone have experience with this type of situation? I am using Grails with Mysql if that is helpful. Thanks

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  • Just for fun (C# and C++)...time yourself [closed]

    - by Ted
    Possible Duplicate: What is your solution to the FizzBuzz problem? OK guys this is just for fun, no flamming allowed ! I was reading the following http://www.codinghorror.com/blog/2007/02/why-cant-programmers-program.html and couldn't believe the following sentence... " I've also seen self-proclaimed senior programmers take more than 10-15 minutes to write a solution." For those that can't be bothered to read the article, the background is this: ....I set out to develop questions that can identify this kind of developer and came up with a class of questions I call "FizzBuzz Questions" named after a game children often play (or are made to play) in schools in the UK. An example of a Fizz-Buzz question is the following: Write a program that prints the numbers from 1 to 100. But for multiples of three print "Fizz" instead of the number and for the multiples of five print "Buzz". For numbers which are multiples of both three and five print "FizzBuzz". SO I decided to test myself. I took 5 minutes in C++ and 3mins in c#! So just for fun try it and post your timings + language used! P.S NO UNIT TESTS REQUIRED, NO OUTSOURCING ALLOWED, SWITCH OFF RESHARPER! :-) P.S. If you'd like to post your source then feel free

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  • Finding if a string is an iterative substring?

    - by EsotericMe
    I have a string S. How can I find if the string follows S = nT. Examples: Function should return true if 1) S = "abab" 2) S = "abcdabcd" 3) S = "abcabcabc" 4) S = "zzxzzxzzx" But if S="abcb" returns false. I though maybe we can repeatedly call KMP on substrings of S and then decide. eg: for "abab": call on KMP on "a". it returns 2(two instances). now 2*len("a")!=len(s) call on KMP on "ab". it returns 2. now 2*len("ab")==len(s) so return true Can you suggest any better algorithms?

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  • What's the best way to implement one-dimensional collision detection?

    - by cyclotis04
    I'm writing a piece of simulation software, and need an efficient way to test for collisions along a line. The simulation is of a train crossing several switches on a track. When a wheel comes within N inches of the switch, the switch turns on, then turns off when the wheel leaves. Since all wheels are the same size, and all switches are the same size, I can represent them as a single coordinate X along the track. Switch distances and wheel distances don't change in relation to each other, once set. This is a fairly trivial problem when done through brute force by placing the X coordinates in lists, and traversing them, but I need a way to do so efficiently, because it needs to be extremely accurate, even when the train is moving at high speeds. There's a ton of tutorials on 2D collision detection, but I'm not sure the best way to go about this unique 1D scenario.

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  • How to detect if a certain range resides (partly) within an other range?

    - by Tom
    Lets say I've got two squares and I know their positions, a red and blue square: redTopX; redTopY; redBotX; redBotY; blueTopX; blueTopY; blueBotX; blueBotY; Now, I want to check if square blue resides (partly) within (or around) square red. This can happen in a lot of situations, as you can see in this image I created to illustrate my situation better: Note that there's always only one blue and one red square, I just added multiple so I didn't have to redraw 18 times. My original logic was simple, I'd check all corners of square blue and see if any of them are inside square red: if ( ((redTopX >= blueTopX) && (redTopY >= blueTopY) && (redTopX <= blueBotX) && (redTopY <= blueBotY)) || //top left ((redBotX >= blueTopX) && (redTopY >= blueTopY) && (redBotX <= blueBotX) && (redTopY <= blueBotY)) || //top right ((redTopX >= blueTopX) && (redBotY >= blueTopY) && (redTopX <= blueBotX) && (redBotY <= blueBotY)) || //bottom left ((redBotX >= blueTopX) && (redBotY >= blueTopY) && (redBotX <= blueBotX) && (redBotY <= blueBotY)) //bottom right ) { //blue resides in red } Unfortunately, there are a couple of flaws in this logic. For example, what if red surrounds blue (like in situation 1)? I thought this would be pretty easy but am having trouble coming up with a good way of covering all these situations.. can anyone help me out here? Regards, Tom

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  • LinkedList.contains execution speed

    - by Le_Coeur
    Why Methode LinkedList.contains() runs quickly than such implementation: for (String s : list) if (s.equals(element)) return true; return false; I don't see great difference between this to implementations(i consider that search objects aren't nulls), same iterator and equals operation

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  • Recursion - Ship Battle

    - by rgorrosini
    I'm trying to write a little ship battle game in java. It is 100% academic, I made it to practice recursion, so... I want to use it instead of iteration, even if it's simpler and more efficient in most some cases. Let's get down to business. These are the rules: Ships are 1, 2 or 3 cells wide and are placed horizontally only. Water is represented with 0, non-hit ship cells are 1, hit ship cells are 2 and sunken ships have all it's cells in 3. With those rules set, I'm using the following array for testing: int[][] board = new int[][] { {0, 1, 2, 0, 1, 0}, {0, 0, 1, 1, 1, 0}, {0, 3, 0, 0, 0, 0}, {0, 0, 2, 1, 2, 0}, {0, 0, 0, 1, 1, 1}, }; It works pretty good so far, and to make it more user-friendly I would like to add a couple of reports. these are the methods I need for them: Given the matrix, return the amount of ships in it. Same as a), but separating them by state (amount of non-hit ships, hit and sunken ones). I will need a hand with those reports, and I would like to get some ideas. Remember it must be done using recursion, I want to understand this, and the only way to go is practice! Thanks a lot for your time and patience :).

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  • Creating an adjacency List for DFS

    - by user200081
    I'm having trouble creating a Depth First Search for my program. So far I have a class of edges and a class of regions. I want to store all the connected edges inside one node of my region. I can tell if something is connected by the getKey() function I have already implemented. If two edges have the same key, then they are connected. For the next region, I want to store another set of connected edges inside that region, etc etc. However, I am not fully understanding DFS and I'm having some trouble implementing it. I'm not sure when/where to call DFS again. Any help would be appreciated! class edge { private: int source, destination, length; int key; edge *next; public: getKey(){ return key; } } class region { edge *data; edge *next; region() { data = new edge(); next = NULL; } }; void runDFS(int i, edge **edge, int a) { region *head = new region(); aa[i]->visited == true;//mark the first vertex as true for(int v = 0; v < a; v++) { if(tem->edge[i].getKey() == tem->edge[v].getKey()) //if the edges of the vertex have the same root { if(head->data == NULL) { head->data = aa[i]; head->data->next == NULL; } //create an edge if(head->data) { head->data->next = aa[i]; head->data->next->next == NULL; }//if there is already a node connected to ti } if(aa[v]->visited == false) runDFS(v, edge, a); //call the DFS again } //for loop }

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