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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How to search for patterns on a (game)board?

Assume a gameboard with two kinds of pieces. Let the task be to find a common patterns of pieces, namely the patterns that lead to winning. The problem is general, but the game in question is ...
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147 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 ...
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211 views

When designing a data structure, should I implement very inefficient operations for convenience?

(I've added the .NET tags because the data structures are for .NET, and this question should be considered in the context of the conventions for that platform.) I'm writing a library of immutable and ...
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2answers
101 views

Add file paths to database

I am scanning a directory of files and want to add them to a database. I have two variants: for file in walk(basedir): files.append(file) for file in files: add_to_database(file) versus ...
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3answers
162 views

Algorithm that generates a group of men and women who are each interested in everyone from the other gender

In my dating app, I need to compile lists of men and women where all of the men in the list are potentially interested in all of the women in the list, and vice versa. That is, in a list of 10 men ...
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2answers
260 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] ...
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3answers
517 views

How to model state of leaving/entering home

I have two sensors: One detecting if the door is open or closed, another if movement has been detected in the corridor. I want to detect if the person has left or entered home. Usually the person has ...
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1answer
132 views

What algorithm can be used to determine order given incomplete information?

Given a series of statements such as: a<c a<b b<c (Read as "a is before b", "a is before c", etc.) What is the order of the elements? In this example, the answer is a<b<c. A less ...
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151 views

Efficient datastructure to create size-limited dictionary

I need a class that acts like a dictionary but will constrain the total number of key/value pairs it contains. For instance, let's say the maximum number of entries is 1000 and the class already ...
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1answer
104 views

Find the best shuffle

I am trying to solve the following problem: Question Description: Given four integer numbers A, B, C, and D, a shuffle of them is a zero-index array, which consists of these four numbers in some ...
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87 views

Algorithm for the Simplication and Evaluation of Equations

As a new programmer messing around in python, I've been playing about with writing small programs which can calculate some of the stuff I did in maths at school. I've been trying to think of a way ...
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2answers
131 views

Counting digits of a decimal number

Is there an algorithm to count digits of a decimal number other than saving it as a string and then looping to find the decimal point and thus count the digits?
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1answer
100 views

What's the algorithm should I use for seeing how well 2 strings match?

Suppose I have 2 strings: string1 = "home/lisa/Music/some_files/01.05 - Garden Ground.mp3" string2 = "Music/Jim Smith/Unknown/(Deluxe Version/Garden Ground).mp3" string4 = "Music/Jim Smith/Unknown/00 ...
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1answer
102 views

More efficient alternative that checks if a list can be made a palindrome

I asked this question on Stackoverflow, but they told me this is the best place to ask. For my algorithms and data structures class, I have to write an algorithm that is more efficient in the worst ...
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1answer
507 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
139 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
149 views

Best algorithm for “ACM ICPC Team”

I have this problem (complete description): There is a list of persons N and M topics. I have to find out the maximum number of topics a 2-person team can know. And also find out how many teams can ...
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220 views

How to determine whether two trees (not necessarily binary) are isomorphic

Two ordered trees T' and T'' are said to be isomorphic if one of the following holds: ◦ both T' and T'' consist of a single node ◦ both T' and T'' have the same number k of subtrees, and the ith ...
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2answers
208 views

String Searching algorithm

A title for a movie can be ambiguous. (Eg. The Lord of the Rings, Lord of the Rings, Lord of the Rings, The) There exists a database entry that has a list of movie titles mapped to a unique ...
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58 views

All clustering possibilities for a graph

Is there a known algorithm for finding all clustering possibilities for a directed graph? EDIT: By cluster i mean a weakly connected sub-graph G, so that E(G) > 0. By a clustering possibility I ...
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1answer
220 views

Program to look at the first say 5 characters of a word and return a string if that string is actually the first 5 characters of a word?

For example, say I have a string and it has the letters: RDNAL This is not an actual English word or it doesn't start an actual english word, so the program would skip this string and would avoid ...
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1answer
106 views

Need an algorithm to filter this collection format

I'm sorry the title is so vague ... I cannot think how to describe it any better. I have a collection in this format: var myCollection = [{id:"a"}, {id:"b",excludes:["a"]}, {id:"c",excludes:["b"]}]; ...
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2answers
159 views

Line intersection detection algorithm

I'm trying to detect if a line drawn by the user intersects itself. I'm using a line intersection detection algorithm that goes through each waypoint of the line and checks if intersects with any ...
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239 views

What algorithm is this?

I have some vague recollections from my algorithms courses, but nothing specific comes to mind. let S be a multiset of things we are interested in. As input, we get T, s1, s2, ... sn, all of which ...
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python: area mapping using trigonometric circle

I have a car controlled by a raspberry pi, I would like to create maps to each place it visits. The solution I came up with is simple. Lets say you tell the car to go forward and then after 5 minutes ...
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1answer
105 views

Algorithm to 'segment' a number into blocks of n?

I'm not sure how to word the title properly, but the problem goes something like this: I have 5 nodes, and node 0 is the "master". User inputs a number, e.g. 100 to the master. master "splits" the ...
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312 views

What algorithm can I use to find the biggest subarray within a 2d array with only n different numbers?

Let's say I have a 2d array 100x100 in size, each cell in that array has a number from 1 to 50 randomly. How do I find the biggest subarray in a rectangle size in that array that has only n different ...
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1answer
121 views

dynamic programming with memoization

I’ve a problem with a programming exercise. I hope you can help me. In this exercise I need to find out what the maximum profit is of taking pictures from several items in a park. For taking pictures ...
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2answers
150 views

Estimating run time of algorithm

For instance if i have an algorithm that is O(n2) and it will run for 10 seconds for a problem size of 1000. Now if i were to double the problem size to 2000 i want to know the approximate run time in ...
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1answer
49 views

Matrix distribution to process grid

I need to write a program, which will perform LU-decomposition, etc. The problem is that I don't know about the preferred way to distribute the loaded matrix from the root process to other processes. ...
3
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1answer
128 views

Algorithm to find minimal set

I have a set of sets S and I want to find a minimal set of elements M such that each set in S shares at least one element with M. S = set of sets ∀ f∈S ∃e · e∈f ∧ e∈M For example: S = {{1}, {1, 2, ...
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384 views

SQL - Algorithm for finding availability of a resource

I'm having trouble creating a mysql compatible algorithm for this. Background App with mysql, perl and JS. It's a booking system where each booking is comprised of a start, end and qty. Start and ...
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36 views

PSO – how Dimensions are set up?

I am coding a Particle Swarm Optimization in C++. I have been for days trying to understand the theory of how dimensions work in each different problem. In the many examples I have seen, all of them ...
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2answers
129 views

Algorithm Space and Time Complexity with Consideration for I/O (eg cache)

Is there an expression of performance for an algorithm or data structure that attempts to consider cache and other hardware concerns? Context: in my class we're looking at binary trees and it seems ...
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Is it reasonable to assume that any physical quantity can be represented by a 64-bit integer without overflow or underflow?

The original binary search algorithm in the JDK used 32-bit integers and had an overflow bug if (low + high) > INT_MAX ...
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MJRTY - A Fast Majority Vote Algorithm isn't work [closed]

The MJRTY algorithm sets out to solve the problem of finding the majority element in a stream (an element comprising more than 50% of the stream). Moore proposed to solve this by using only 2 pieces ...
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2answers
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Which way is more efficient for getting the space count?

I have just started reading Cracking the Coding Interview. One of the problems (specifically 1.4) after solving and then looking at the answer made me question the way it is done and decided to post ...
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1answer
65 views

timed events to modulation of real-time audio

I am new very to audio programming and am having trouble figuring out the right kind of algorithm for converting control events (e.g. like MIDI) to real-time sound genesis with a buffer. At the ...
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1answer
111 views

Connected components of undirected graph

Suppose I have an undirected graph G with vertices v1...vn and edges. Right now it is in adjacency list representation. For every time moment I have as input some subset of vertices that are "active" ...
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A fast algorithm for a simple multi-objective minimization?

I have a set of n (arbitrary) integer numbers S which I want to partition into k subsets S_i each of size n/k (you can assume that k divides n). Let A be the arithmetic mean of elements of the set S. ...
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1answer
82 views

Should changes to FNV-1A's input exhibit the avalanche effect?

This is kind of related to Which hashing algorithm is best for uniqueness and speed?. In that question, the excellently written top answer notes, Randomnessification The other subjective ...
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1answer
202 views

Would adding more digits be a way to scale a order generation service? [closed]

I am working on interview questions from Amazon.com Software Development Engineer Intern Interview Questions. One of the interviewees was asked "give a scalable system design of Amazon.com's order ...
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2answers
154 views

c++11 random: why different range of int and real?

In the c++11, we now have <random> to produce random number. About uniform distributions, we have following int_distribution and double_distribution: uniform_int_distribution-produces integer ...
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173 views

What is a formal definition for an algorithm step?

Consider the following code to find the K th minimum element of an array: FindKthMin(A[], k) { A = Sort(A); return A[k]; } Could it be an algorithm without specifying the sort details? ...
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335 views

What benefit is there to using recursive binary search over iterative binary search or vice versa?

In a recent assignment for my programming 2 class we tested the efficiency of searches by populating a java ArrayList with 13,040 strings. The sequential search was obviously slower than the binary ...
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35 views

Finding the largest bundle of flagged points

I am currently working to develop a program that takes in an array of 4 columns and around 200,000 rows. Each column represents x, y, z (coordinates), and a flag denoting whether or not this point is ...
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287 views

How to iterate through all permutations of valid links between nodes

Imagine a 2D area, with a number (array) of nodes (or points) defined within it, in arbitrary (but known) positions (integer x,y coordinates), like this: From there I want to be able to, ...
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303 views

Abstraction in algorithms

I asked some questions about algorithms, and some replied they are abstract concepts, however I don't know what abstraction means for algorithms or how it applies. For objects, I know if we remove ...
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1answer
317 views

What is the most efficient / fastest way to keep a list in order?

I implemented Dijkstra's path finding algorithm in JavaScript and a big part of it involves storing the distances to nodes and fetching the smallest. The distances change often and the smallest is ...
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2answers
282 views

Is recursion a declarative approach to solve the problems?

I have noticed many problems in algorithms textbook are solved by recursion (divide and conquer, backtracking,...) As I tried to enhance my skills in writing them, I have noticed, I just need to ...