In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning.

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3
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81 views

Graph visualization algorithm

I need a 2d or 3d graph visualization algorithm by which adding/removing a node or a relationship does not have a butterfly effect on the positions of other nodes. (We are talking about a directed ...
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1answer
77 views

Sorting a large number of unknown items with multiple stacks

Here is a problem I'm trying to solve for a personal project. I'm not exactly sure how best to even approach it. Problem: I have a single stack already populated with several thousands of unknown ...
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2answers
148 views

Some people told me that finding all prime factors of a number is an unsolvable problem. Is that real? [closed]

I'm a beginner, so I spent a lot of time trying to solve the 3rd problem on projecteuler.net, which is: "Find the largest prime factor of 600851475143" Now, I imagined it would be more useful if I ...
3
votes
2answers
151 views

Is it possible to speed up a hash table by using binary search trees for separate chaining?

I want to implement a Hash Table using Binary Search Trees to reduce the search complexity in the Separate Chaining process from O(n) (using linked list) to O(log n) (using BST). Can this be done, and ...
2
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2answers
88 views

MaxHeap-like data structure supporting max AND min, also decrease-key (yes decrease-key)

For the purpose of implementing an optimization algorithm (finding the minimum of a multivariate function) I want to create a data structure that supports the following operations: load from array ...
0
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2answers
115 views

Is studying algorithms important for game development? [closed]

I am fairly new in the programming world, I have a 1-year experience and I learned by watching online courses, and I made few iOS apps. Now I am moving into game development and I already ...
1
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3answers
214 views

Check distance between all elements in a list of numbers in O(n*lg(n))

I have an exercise for my algorithms and data structures class, where I basically have to implement a divide and conquer algorithm or function called check_distance to determine whether all numbers in ...
2
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3answers
206 views

Close to knapsack problem?

I think that I am trying to solve a problem somewhat similar to a knapsack problem. I am not sure though. Please see the input given below and my solution. There are three types of items and 4 ...
-2
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1answer
63 views

Pairing 40 people over 20 days such that no pair is the same twice or more [duplicate]

I'm trying to figure out what algorithm / method I can use to figure out how to pair people together such that the pairs aren't repeated i.e. if a unique individual is denoted by Px where x is their ...
2
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0answers
86 views

Smallest number of rectangles covering marked parts of grid

I have an N by N grid of cells, and certain blocks are marked: +--+---+---+---+ | | | | | | | x | x | | | | x | x | | | | | | | | | | | x | +--+---+---+---+ I would like to ...
1
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1answer
127 views

Increment or double problem

I have a problem with an assignment. In this assignment I have to create a program which needs to calculate how many different possibilities are there to get from number a to b. To get from a to b you ...
5
votes
1answer
238 views

Compute Adjacent Pair

I was given the following problem: Integer V lies strictly between integers U and W if U < V < W or if U > V > W. A non-empty zero-indexed array A consisting of N integers is given. A ...
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1answer
145 views

What algorithm-family or problem-space description fits? Industrial process feeding ingredients to process

Our process continuously feeds (normally <= 8) ingredients from a choice of hundreds, using 3 feeders only. So if ingredient count X is > 3, 3 through X are stirred together in a batch process and ...
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0answers
53 views

Combining items from several lists with pagination

I am trying to come up with an algorithm for getting items for a news feed from several sources. There are multiple lists of data: S1, S2, ... Sn. Each of these lists has a certain known amount of ...
2
votes
3answers
189 views

fast, say O(log2(N)), sliding median algorithm

So I know how to do a fast O(log2(N)) sliding max or sliding min algorithm. Brookes: "Algorithms for Max and Min Filters with Improved Worst-Case Performance" IEEE TRANSACTIONS ON CIRCUITS AND ...
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4answers
163 views

List comparing techniques for faster performance

I need to cross names from two lists, and find all occurrences of one name in the other. The lists are too big, one have 50k elements and the other 400k. For a small list I would use two foreach ...
0
votes
1answer
36 views

Split multiple overlapping intervals to non overlapping intervals

currently I try to build an algorithm to split an array of overlapping intervals to a new array with non overlapping intervals. For example: Array of overlapping intervals: [ {0,7}, {8,12}, ...
1
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1answer
93 views

Non-fixed-size Fenwick Tree implementation

I'm planning to implement a non-fixed-size Fenwick tree. That is, a Fenwick tree that allows interleaving range queries with adding/removing elements. All implementations and samples I've seen so far ...
0
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5answers
494 views

Fastest way to determine if a value is in a list?

I'm aware there may not be a good solution to this problem. I'm looking for a fast algorithm that determines whether or not a value (let's say an integer) exists in a set of values, however I need the ...
0
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1answer
65 views

Translation algorithm - combinations to indices

I have a deck of 52 poker cards represented as array of int - [0, 1, ... 51]. There are 2.598.960 possible combinations of 5 cards. I can generate all combinations like this: #id #combination ...
0
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0answers
50 views

scrabble solving with maximum score

I was asked a question You are given a list of characters, a score associated with each character and a dictionary of valid words ( say normal English dictionary ). you have to form a word ...
2
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1answer
247 views

Solving a Sudoku variant with an unknown element

I recently stumbled upon a special Sudoku variant and am now struggling to effectively solve it programatically. Consider the following initial 6x6 grid: The rules The red question mark is ...
16
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8answers
5k views

Is having trouble with data structures common for beginners? [closed]

I'm taking my second course on Java. We are getting into data structures. I have done an assignment on a linked list, and now a stack. I had a hard time with the linked list. The stack gave me a ...
1
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1answer
175 views

Calculate Big-O for nested for loops

I found this nested loop to calculate the Big-O notation. for(i=0;i<n;i++) for(j=0;j<i*i;j++) for(k=0;k<j;k++) I got the time complexity for the algorithm with this polynomial ...
2
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2answers
797 views

About insertion sort and especially why it's said that copy is much faster than swap?

From Lafore's "Data Structures and Algorithms in Java": (about insertion sort (which uses copy + shift instead of swap (used in bubble and selection sort))) However, a copy isn’t as time-consuming ...
678
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9answers
227k views

Which hashing algorithm is best for uniqueness and speed?

Which hashing algorithm is best for uniqueness and speed? Example (good) uses include hash dictionaries. I know there are things like SHA-256 and such, but these algorithms are designed to be ...
3
votes
1answer
241 views

Efficient algorithm for Virtual Machine(VM) Consolidation in Cloud

PROBLEM: We have N physical machines(PMs) each with ram Ri, cpu Ci and a set of currently scheduled VMs each with ram requirement ri and ci respectively Moving(Migrating) any VM from one PM to ...
0
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0answers
14 views

Polling more recent / active items more frequently

I'm setting up a service that is meant to query, via a rate-limited API, a number of posts in real-time. Now, some of these posts can be several months old, and they should really only be queried, ...
0
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2answers
89 views

Average number of comparison for sort algorithms

I need to write different sort algorithms such as bubbleSort insertionSort selectionSort quickSort mergeSort And measure how many average comparison does each one for N number (averaging between ...
2
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3answers
905 views

Algorithmic problem: Picking Cards

The problem below appeared on the last Code Sprint 2 programming competition (it's over already). The base cases are clear, but developing an algorithm that solves all possible cases has been a ...
0
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2answers
316 views

Just in time prize winning algorithm [closed]

I'm building a contest where you can win prizes by opening boxes. Whatever the box is open, i just send a request to the server to test if the user won something. Since this contest is not a "Register ...
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votes
1answer
111 views

How to selecting Teams with Minimum Difference between Knowledge Levels

For the below challenge from a programming site, I am bit confused. Problem Statement: A Professor of Physics gave projects to the students of his class. The students have to form a team of two for ...
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1answer
144 views

Estimed number of tries

Problem: The Oscar Committee wants to decide which person should get the best actor award among the given N actors.For that they decided to use a random function random_bit() which returns either 0 ...
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1answer
200 views

Optimal movie schedule

Let's say Mr. A goes to cinema and he gets a movie schedule. There are N movies on the program today (1 < N < 50) and for every movie the time of the start and the time of the end are given in ...
7
votes
3answers
773 views

Apple eating problem

Player A and Player B play a game. On the middle of the table there is a pot full of N apples of different weights. Player A starts first and choose an apple and start eating it. Losing no time player ...
30
votes
5answers
5k views

Champaign Fountain Puzzle

Empty glasses of water are arranged in the following order: When you pour liquid into the 1st glass if it's full, then the extra liquid would be flown into the glasses 2 and 3 in equal quantities. ...
0
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1answer
691 views

Puzzle solving: Minimum number of steps to achieve a goal

I have been doing some programming contest problems, and I have noticed that many of them involve something along the lines of "get the minimum number of steps necessary to achieve a certain goal". ...
3
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5answers
469 views

Which mathematical properties apply to XOR Swap algorithm (and similar bitwise operator algorithms)?

Assume you have two variables a and b, and you need to swap them, and for whatever reason, making a temporary variable for storage is not an option. This is the algorithm in pseudocode a ← a XOR b b ...
0
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2answers
137 views

Is there a approximate string comparison function which is odd like mathematical functions are odd?

I say odd like a mathematical function, a mathematical function is odd if f(-x) = -f(x) I understand that comparing two strings may seem to have little to do with this, because the arguments cannot ...
5
votes
1answer
281 views

Does anybody recognize this scheduling problem? Is there an algorithm for it?

Consider the following problem: Description: There are n jobs J1...Jn with cycle times C1....Cn. Find a time quanta and a scheduling table considering that: any element of the table contains at ...
2
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0answers
93 views

Asking questions to the user based on results of previous questions

I have to select a question that would help me make me sure the user knows about a given subject. As an example, let's assume the user hasn't answered any question yet. Every question has a scope ...
0
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3answers
154 views

Does it really need to convert decimal,string, etc to binary?

I'm very new to programming. Just read some articles about algorithm for converting a decimal or string to binary. But,according to what I know, computers hold these data in binary form. So why don't ...
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0answers
49 views

Compare names and the use of Levenshtein's algorithm

I need to cross names from two lists. What is the best away to compare the names? As you may expect, in one list we can have the complete name, on the other just the first and last. Besides that, ...
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1answer
84 views

How to count sort comparison

When it is said that this sort has M number of comparisons what does it mean? As an example: procedure bubbleSort( A : list of sortable items ) n = length(A) repeat swapped = false ...
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4answers
270 views

algorithm to extract “possibilities” from a tree

From a given tree, subsequent trees have to be generated. Nodes can be marked as "variant" in the given tree (the example uses an asterisk to mark the node). All possible combinations between the ...
7
votes
6answers
1k views

Algorithm to generate N random numbers between A and B which sum up to X

This problem seemed like something which should be solvable with but a few lines of code. Unfortunately, once I actually started to write the thing, I've realized it's not as simple as it sounds. ...
3
votes
2answers
210 views

How to draw rectangles for 2D arrays

I have an 2D boolean array that looks like this: [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][1][1][0][0][0][0] ...
2
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2answers
219 views

Dynamic Programming Problem - To find smallest integer number 'x' which contains only digits 1's and 0's such that x mod n = 0

To design an algorithm that will output the smallest integer number 'x' which contains only digits 1's and 0's such that x mod n = 0 and x > 0..... For example: 2 divides 10 3 divides 111 4 ...
0
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1answer
196 views

Turn over cards in minimum number of steps

Imagine you're given an array of cards. Some of them are facing down (0), while some of them are facing up (1). Is it possible for given fixed K to turn all the cards face-up by turning over any K ...
2
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0answers
63 views

Can't figure out class scheduling issue? [closed]

"You are a college advisor trying to help students plan their academic careers. You have the list of courses in each major and their prerequisites. Students often want to take their major courses as ...