# Tagged Questions

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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### 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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### 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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### 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, ...
314 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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### 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 ...
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### 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. ...
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### 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] [0][0][0][1][1][1][0][0][0]...
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### 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 ...
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### 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 ...
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### Given a subset of numbers and subset of sums. Match the numbers to sums.(Harder than appears)

I'm not sure what the most efficent solution to this algorithm is. I'm not sure this fits exact cover, and approaching it via exhaustive backtracking seems somewhat inefficient. Any suggestions on how ...
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### 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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### Reduce a list of IPv4 to lowest common CIDR

I have a long list of IP addresses that show some pattern of closeness Example: XX.249.91.16 XX.249.91.21 XX.249.91.32 XX.249.91.160 XX.249.91.165 XX.249.92.15 XX.249.92.25 XX.249.92....
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### Karger's algorithm for bin-packing?

I first came across that algorithm as the "Random minimum cut" algorithm. And recently a colleague was trying to pack a big quantity of small textures into one image file. Then it clicked - why not ...
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### What would be the Impact of P=NP? [closed]

I am preparing for a test and I can't find a clear answer on the question: What would be the impact of proving that PTIME=NPTIME. I checked wikipedia and it just mentioned that it would have "profound ...
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### Converting a bounded knapsack problem to 0/1 knapsack problem

I ran across a problem where goal was to use dynamic programming (instead of other approaches). There is a distance to be spanned, and a set of cables of different lengths. What is the minimum number ...
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### Java and .NET: Why different sorting algorithms are used by default?

Just wondering why Java and .NET Framework uses different sorting algorithm by default. In Java Array.Sort() uses Merge Sort algorithm by default and as Wikipedia.com says: In Java, the Arrays....
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### 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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### 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 ...
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### Time-complexity of nested for loop

I have loops like this: for(int i = 0; i < n; i++) { for(int j = 0; j < i; j++) { sum += 1; } } It's O(n * ), but I'm not sure what the j < i loop is. I have some tests ...
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### 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 ...
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### General Way to convert a loop (while/for) to recursion or from a recursion to a loop?

This problem is mainly focusing on the algorithm, maybe something abstract and more acedemic;) The example is offering a thought, I wanna a generic way, so example is only used as to make us more ...
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### Ant colony algorithm

I am a student working on an ant colony simulator for a course project. The algorithm for it is (obviously) an ant colony algorithm. I know there are various forms of the algorithm but all of those ...
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### Algorithm for detection of overlapping between vectors

I am currently developing a math-physics program and I need to calculate if two vectors overlap one another, the one is vertical and the other is horizontral. Is there any fast algorithm to do this ...
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### Using Euclidan Distance to intialize centroid of K-Means

I need to initialize centroid of K-Means using Euclidan distance. Is it possible? If so how the algorithm should be? I have been stuck for a while and couldn't figure it out. Thanks for your time.
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### Render order of two-edge directed node graphs

I'm trying to find an algorithm for graphs with the following contents: Nodes with no edges leading out of them (shown here as a red circle) All other nodes have exactly two edges leading out (...
10k views

### Quicksort and middle pivot

I am having a head ache understanding quicksort with middle pivot. I found lot of explanations about using left most or right most, but not many about a middle one. Can I safely assume these?: If ...
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### An algorithm for finding converse duplicates of ordered pairs

Given an array of ordered pairs of values, what algorithm will find converse duplicates? [Converse meaning the same values, but in the opposite order.] That is, given [ab,ac,ad,bc,bd,ca,db] is there ...
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### How can I approach creating an efficient algorithm for maximizing value with these specific constraints?

I'm having trouble coming up with an approach that isn't n^2 for this problem. Here's a contrived, simplified version I've come up with: Let's say you're a company that needs 4 employees to launch in ...
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### 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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### 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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### elevator algorithm and implementation [closed]

I wanted to know how (real) elevators work. But, so far, I could not find much material about the algorithms they use, nor software (if any) for simulation. Could anybody give me references for that?
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### equal distribution within given set of users

I have a requirement where I have a list of entity and users who that entity can be assigned E1 can be distributed by U1 or U2 E2 must be distributed by U5 E3 can be distributed by U2 ...
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### Creating algorithms [closed]

I am a relatively new programmer. I can pick up languages and learn syntax at a speed that I consider good, but I can't figure out how to solve problems logically using algorithms very well. I know ...
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### Is there any better approach to shortest path finding within a (vehicular) traffic network?

Dear fellow programmers, We're developing software which simulates vehicular traffic. Part of the process called "assignment" is concerned with assigning vehicles to their routes and has to use some ...
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### 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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### Finding the shortest path through a digraph that visits all nodes

I am trying to find the shortest possible path that visits every node through a graph (a node may be visited more than once, the solution may pick any node as the starting node.). The graph is ...
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### 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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### 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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### 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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### Is Bubble Sort the slowest sorting algorithm? [closed]

Is bubble sort the least Big-O efficient? If the answer is no, then what is the least efficient sorting algorithm?
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### 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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### 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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### Algorithm for matching similar content text items

I am working on a website (C#, ASP.Net MVC 3) which reads some RSS feeds from multiple sources and put feed title and summary in a database table(Sql Server). What I want to do is: Put an algorithm ...
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### Algorithm for a UI showing X percentage sliders whose linked values always total 100%

A system I'm building includes a set of UI sliders (the number varies) each with a scale of 0-100. By slider I mean a UI where you grab an element and drag it up and down, like a volume control. They ...
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### 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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### 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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### 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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### 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 ...