# 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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### Keeping track of the number of nodes in the subtree in black and red trees

I was wondering, if I have a black and red tree and I want to keep track of the number of nodes in the subtree, what is the most effective way to do so? I mean how do I work with these values while ...
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### Finding all possible ways of inserting a pattern into a string

I've been thinking about this problem for a while, and I can only find a recursive solution but I'm feeling that there is a dynamic programming way to do it, I just can't figure it out. Is this a ...
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### How to match up courses with requirements

I have a list of courses taken by a student, as well as several requirements. Each requirement consists of a list of courses that fulfill that requirement and the number of such courses that must be ...
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### List all intervals made by inherited array of intervals

i have a grading system which works like this: You have a array of intervals with grades: [9, Inf) => A; [7, 9) => B; ... (-Inf, 1) => F But you can create also inherited grading system ...
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### Neighbourhood points (2d)

I have a 2d coordinates system with some points on it, like this one: Now I am looking for an algorithm (or just some approach) to find neighboured points. So, if you have the coordinates of one ...
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### Determine what to draw based on neighbour tiles?

I have a tilemap and I want to add walls to it. I painted 16 images, one for each possible combination. For example: A lone wall tile would get a image that has walls around. A corner would get ...
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### Extract significant locations from GPS readings

I'm writing an app that continuously monitors user location 24 hours a day using a mobile phone with readings every 5-30 mins (about 50-300 readings a day). How do I cluster readings and extract user ...
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### How to find the closest vector to a given vector?

Let's say I have several points / vectors (in 2D to keep it simple, but could be of any dimension) [x1, y1] [x2, y2] [x3, y3] .... [xn, yn] If I pick some point [x', y'], how do I ...
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### Generate pips on a die based on value

Is there an algorithm to generate the pips on a die or domino? I know that there is usually an odd number of columns and even number of rows (unless the max number of pips is not a perfect root). ...
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### Why do textbooks use pseudocode rather than real languages?

In colleges and in algorithm textbooks, it is quite common for the teacher and author to explain control flow in pseudo-code. With the advent of more expressive languages like Python and Haskell among ...
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### Algorithm to detect if a list of strings need delimiters

I need to write a function to detect if a set of strings needs delimiters when concatenated in any order. For example, the strings ("A","B","C") do not need a delimiter: "ABCBB" -> ["A","B","C","B"...
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### Patching data by identifying and copying repeating pattern

I have a dataset sampled with a specific pattern (timestamps). The very first repetition of the pattern is damaged, meaning that the values are nonsense. To exemplify, my data looks like this: data = ...
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### Sorting algorithm for Provides/DependsOn objects

I have a set of type rewriters, each modifies a given C# type in a different way. Examples are: Add the XYZ attribute to each property of the class Add an ID property Add two properties and some ...
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### Merge sort and O(n log n) mystery

I read every explanation here but still not convinced. I think mergesort is n * n and I know I am wrong but not sure where. Here is what I think: Suppose we are sorting 8 elements and this is the ...
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### How to calculate winning chances of one poker hand against another? [closed]

My question relates to Texas Hold'em Poker. But I believe it will be the same algorithm for any kind of poker game. So let's consider two hands: AJo and KQo. I can use online calculator and find out ...
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### What is the meaning of “static” in pseudo-code

This is a pseudo-code from "Artificial Intelligence: A modern approach" function Table-Driven-Agent(percept) returns action static: percepts, a sequence, initially empty table, a table, ...
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### Find missing number in sequence in string [closed]

I have a string that contains numbers in sequence. There are no delimiters between numbers. I have to find missing number in that sequence. For example: 176517661768 is missing the number: 1767 ...
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### How to “de-dupe” similar lines (detected using the Hough Transform as rho/theta pairs)

I'm trying to identify an object (a cube) in a set of photos. Using Canny/Sobel/Hough I've managed to get the photo down to a set of lines that are pretty accurate; however if I plot these lines on my ...
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### Extract the main entity from a body of text for text categorisation?

I'm trying to categorise products based on various fields of data. I've had some success just matching search terms in the product names, but this naive approach doesn't work when it comes to larger ...
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### Algorithm to get all possible forms of a word with varying suffixes [closed]

I'm writing an application in javascript where given a word, I need to get all the possible versions of the word with the suffix being the difference between each form. For example: "sponsor" should ...
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### Selecting a CPU or microcontroller needed for a given software application?

Say I had a software algorithm (for example, an FFT), and I need it to process (n) amounts of data in (t) milliseconds. This is a real-time task written in C. There are a lot of CPUs out there, and ...
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### Considerations when making data structure and algorithm choices [closed]

What are some reasons you may choose a worse runtime algorithm? And what are some advantages of a linked list vs a hash table/array where access is constant time.
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### Implementing CMA-ES

I am attempting to implement the CMA-ES optimization algorithm in my favorite language (using the example code here as a guideline), but I need help solving a problem I am having. To test the ...
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### Word game algorithm

Back in the days of 8-bit machines there existed an educational word game. I have no idea what it was actually called but for the sake of this question (since it involves pyramids) let's call it ...
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### Find minimum number of steps to a goal without estimator for how close intermediate steps are to the goal

I've been trying to find a good way of solving the following problem, but I'm not sure how to even frame it. I think there might be relatively well-known solutions I'm not familiar with, since I don't ...
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### Generate equally sized areas in polygon

I am looking for a pseudo code logic that would find n equally sized areas in a given polygon. No space should be between or outside the matched areas. First valid match of areas should be returned. ...
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### Polygon simplification that encloses original set of points

I have been trying to implement an optimization for 2D sprite rendering to fight the problem of limited fillrate on mobile devices. The idea is to render textured polygons instead of quads that will ...
209 views

### Find all paths in a tree type of structure

The language I am using is C#, but I am looking more for help with the algorithm more than I am concerned with which language. I have been trying to develop this algorithm for a while now and I can't ...
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### How to approach hours forecasting

I need to forecast budgeted hours for 2 departments to help them schedule staff as currently the best they can do is just wing it. When we receive a job proposal I'll have the person submitting the ...
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### Divide the world map into fixed sized blocks

I am developing an app where I need to divide the entire world map into fixed sized square blocks. For simplicity, think of it as a problem of dividing the google maps into a fixed sized block. I can ...
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I've ran into a problem trying to calculate prorating of a service. Hoping to get some help/hint from the community. I apologize if this isn't the right place to ask this question - will appreciate ...
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### Finding similar high dimensional vectors

I have two lists (sizes m and n) containing high dimensional bit-vectors. All vectors have the same number of dimensions and use Hamming distance as measure if distance. For each element in the first ...
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### Optimization problem where to start, what algorithms to use? [closed]

I have an optimization problem and I was wondering where to start from to be able resolve it. I think it can be solved with an NP-complete algorithm but I am not sure where to start from. The problem ...
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### Retrieving an incorrectly stored tree data structure

Way back in the hazy origins of our platform it was decided that we were going to need some hierarchical data structures stored in the RDBMS. The relationships between nodes were stored via a '...
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### Improving sampling algorithm

I am having a bit of trouble designing a new feature at the moment. It is part of a resource management system. I was wondering if anyone has experience doing anything similar. I'll try to explain: ...
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### JavaScript functional conversion from flat list to tree

I've been going through the RxJS tutorials http://reactivex.io/learnrx/. Almost all of the exercises involve moving from a hierarchical structure to a flat structure so I thought I'd try to do the ...
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### Generate quantity distribution of objects to reach goal for each attribute

The Problem Suppose we are given a variable-length list of objects containing a fixed-length list of positive decimal numbers as attributes. JSON Example [ {a: 0.1, b: 0.6, c: 0.0}, {a: 1.0,...
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### Name-Based Sorting Algorithms For Maximized Common Letters

I am attempting to write a program for a competition (we're allowed to consult Stack Exchange, as long as I'm not given physical code) that takes in a list of 5000 people's names (distributed fairly ...
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### Algorithm to get all paths in a tree

I have a tree that has n-levels. For example here I have four levels: Each node has two children (except for the last one), however everyone except for the first and last node of each row has two ...
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### Is this Red-Black tree insertion pseudocode from Introduction to Algorithms (CLRS) correct?

For the Red-black tree insertion fixup the book distinguishes between 6 cases, 3 of which are symmetric. The cases are (z is the node being inserted): Case 1: z's uncle is red Case 2: z's uncle is ...
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### Algorithm to generate Edges and Vertexes outwards from origin with max multiplicity of 3

I am creating a 2d game for a website where the universe can grow extremely large (basically infinitely large). Initially, the universe is composed of 6 stars that are an equal distance from the ...
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### Should I be using any algorithm to sort/find items, or use a language's built-in ways?

I'm currently a first semester IT student, and I'm wondering if it's better to write my method to find something e.g. in a C# List, or to use any built in method to do these, such as LINQ or .Find or ....
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### How to design a function that takes a date and gives out a number between 1-6, always the same for all dates

As a part of an algorithm I'm making I need to make a function that takes the current date to a function and gives out a number between 1-6, and not the same number for two consecutive dates. And it ...
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### Create arithmetic expression from number using +-/* that equals target [duplicate]

For example, you are given the source 1234 and the target 24. The task is to use the standard arithmetic operators +-/* placed within source, without changing the order of the digits of source to ...
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### Find path of steepest descent along with path length in a matrix

Came across this problem -- You are given a grid with numbers that represent the elevation at a particular point. From each box in the grid you can go north, south, east, west - but only if the ...
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### What is a lattice parser?

My friend asked me for help with his task: "Redeem a lattice parser with any programming language" - the problem is that he can't clearly explain me how the lattice parser should work. I've tried to ...
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### Efficient algorithm to merge n successive sorted arrays in place

I am developing an in-place sorting algorithm that leaves the array into a state where it is basically a succession of sorted subsequences of any size (most are bigger than log2(size(array))); then it ...
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### Do you know the name of this algorithm? (cycle with history?)

Context : I'm a IT student who is trying to implement a small application for my family. Every year, we offer each other gifts. Each one of us pick a name of a family member in a hat, and have to ...