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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“Hand written” recursive descent parser with “catch all” rule

I'm trying to write a (scannerless) recursive descent parser with a "catch all" rule for the following "Mustache template" grammar (simplified here): content : (variable_tag | section_tag | ...
3
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3answers
157 views

What is the most efficient way to find a set of locations within a radius of a certain point?

Imagine a dataset of all the restaurants in the US (similar to Yelp, etc), how would you return a set of restaurants within a certain range of a particular zip code. (Assuming you have already a ...
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3answers
90 views

Avoid numeric errors in Naive Bayes method

I am implementing the Naive Bayes method with Gaussian distribution. The problem that I have is that the variance used on the Gaussian curve (calculated from a training set) is REALLY small. They ...
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1answer
239 views

Kth selection routine - Floyd Algorithm 489

I have recently come across a promising Kth selection routine that reportedly outperforms quickselect the Floyd, Rivest Select routine. This Wikipedia article provides a pseudocode version which I ...
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3answers
136 views

How to determine if set of ordered coordinates form a simple curve?

I hope it is the right place to ask this. I wasn't sure if it belongs to Stack Overflow or Computer Science. Eventually this seemed more suitable. Anyway, some background first: A closed curve, is ...
2
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2answers
197 views

How to iterate between these elements

I have an array of elements: int[] elem = new int[] {A, B, C}; I need to calculate the sum of ALL the combinations of those elements, where only some of the elements can be optionally selected. I ...
0
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1answer
178 views

I need a data structure for a card game

I am programming a card game in java, and unsure what data structure I should use for the player's hand. I considered using an array, with one integer to traverse the array and another integer to ...
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1answer
119 views

Big O notation of randomness

I was thinking about inefficient algorithms based on randomness and wondered how to categorise them. For instance. Say you wanted to generate all the numbers from 1 to N in a random order but only ...
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2answers
206 views

Algorithm to detect if a word is spelled correctly

I am trying to develop a javascript spellchecker that doesn't use a dictionary, and can correctly, given a single word, detect if a word is spelled correctly or not. Right now, I just have a list of ...
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2answers
329 views

What algorithm should I use for a lot of if else(s)?

I have to implement a lot of if else statements and I'm thinking of using Decision Tree but I'm not sure if it's going to be the right algorithm. I don't want to insert a piece of html code based on ...
4
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3answers
247 views

GPLing an implementation of a patented algorithm

TL;DR: Can you publicly release your own implementation of a patented algorithm as a free research tool for others, under the GPL, when you do not hold the patent (but will happily give clear and ...
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0answers
138 views

Is this a Bin Packing Problem?

Let us consider we have B Bags and each Bag has some number of Items. The problem is to distribute Bags of Items uniformly across as minimum number of Bins as possible. However, there are two ...
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2answers
250 views

Looking for the name of an algorithm (or technique)

I am searching for an article on the net which I can't find anymore. It was describing an algorithm to rank web pages. I am trying to remember the name of this algorithm or technique. The principle ...
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1answer
101 views

Decision tree (?) reduction

I need to check certain conditions (of size n) on an object and perform one of several options available (size m) based on the result. Seems to me it fits a tree. Now. The tree is quite large and I ...
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1answer
74 views

Build odd and even hanoi tower [closed]

I've got problem with hanoi tower. I know how to build normal hanoi tower, it's simple: void solveTowers(char src, char dst, char mid, int n) { if (n == 0) { return; } ...
4
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1answer
123 views

Algorithm to find whether there is a path (any path) above length X between two vertices

We all know how to find the shortest path between two vertices, but what if I just want to know the answer to this question - is there a path, (any path), between vertex A and B of length larger than ...
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0answers
34 views

Best and simplest way to implement a double ended priority queue with insertion and find operations lg(n)?

What is the best way to implement a double ended priority queue with O(log(n)) complexity of insertion, find min and find max operations? I was thinking to implement a red black tree, but it is a ...
5
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1answer
210 views

Python rectangle packing

I'm working on a project which involves packing multiple rectangles in a larger rectangle(the bounding box). Rectangles can't overlap with each other or with the boundaries of the bounding box. ...
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2answers
78 views

Efficient range search for pair of numbers

Assume we have large list of pairs: struct {x: double, y: double} pair; vector<pair> What is the most effective way to find all pairs where (x1 < x < x2) AND (y1 < y < y2)? O(n) ...
5
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1answer
126 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 ...
5
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2answers
221 views

Algorithms for allocating N balls into M boxes

Every box has at least no balls and at most N balls. Of course the total number of balls in M boxes must equal to N. For each allocation, I calculated a value based on the allocation: ...
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2answers
163 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 ...
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2answers
186 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 ...
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1answer
110 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
143 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 ...
2
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2answers
95 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 ...
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3answers
66 views

Algorithm to generate parallel path inside polygon

A path is defined as a list of 2D points (x,y) (and may be open or closed). Given a path p, what is an algorithm which generates a path p' which is "inside" p and at constant offset to p i.e. each ...
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1answer
79 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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3answers
219 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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0answers
98 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 ...
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1answer
131 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 ...
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0answers
61 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 ...
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1answer
70 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}, ...
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4answers
196 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
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1answer
73 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 ...
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0answers
54 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 ...
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5answers
519 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 ...
2
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3answers
215 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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1answer
222 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 ...
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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, ...
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2answers
143 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 ...
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0answers
64 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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3answers
159 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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1answer
99 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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2answers
108 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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0answers
95 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 ...
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9answers
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Big O Question about an algorithm with (n^2 + n) / 2 growth rate

I'm asking this question because I am confused about one aspect regarding big O notation. I am using the book, Data Structures and Abstractions with Java by Frank Carrano. In the chapter on the ...
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1answer
64 views

Pathfinding in a 3d world with obstacles?

What are some methods for pathfinding in a 3d world? Object X needs to move from Point A to Point B but it might have to avoid things like asteroids, planets or gas pockets that makes the object ...
3
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1answer
73 views

Consistent snapshot

Suppose process A has a consitent snapshot of some entities. And it is constantly receiving updates for this enteties. Now client B connecting to A and it should receive the consistent snapshot of ...
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0answers
43 views

Can't figure out how to parallelize the calculation of the amount of offspring expected for species in genetic algorithm

I developed a genetic algorithm in java 8 taking advantage of its reasonably free parallelism opportunities with Streams. As you are likely aware, running the epochs takes its time for even a test ...