Questions tagged [matrix]

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7 votes
1 answer
426 views

Smallest Rubik's cube state representation

I'm trying to determine what is the fewest number of bits I need to represent the state of a Rubik's cube. (EDIT: I am assuming the cube is a valid Rubik's cube that has not been altered and only ...
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  • 89
4 votes
3 answers
2k views

What is the most effective algorithm to evenly distribute n points on a 2 dimensional array so they are as separated as possible?

I am trying to code a game which currently uses a matrix ( that I am calling a map). On this map are islands which can be generated n times. The purpose of the algorithm is to distribute the islands ...
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1 vote
1 answer
142 views

What is the most efficient way to represent resizable adjacecny matrix

I'm building a simple app that represents some matrix, where nodes are added quite often. Currently I have following code for adding a new node: let mut new_edges = Array2::default((position + 1, ...
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4 votes
5 answers
458 views

How to measure the solution level of an unsolved Rubik's Cube?

I am trying to figure out how to measure the relative success level of a given (but unsolved!) Rubik's Cube state. My first idea was to calculate the number of overlapping "cells" in the destination (...
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  • 149
0 votes
0 answers
121 views

Quick way to check if there is a path in digraph

I have a finite directed graph (of several weakly connected components). Having two elements I need to check if there is a path from the first one to the second one. The easiest solution is to ...
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  • 722
2 votes
3 answers
297 views

What Behavior would most users expect from a "Row Iterator" and a "Column Iterator"?

Let's say I have a Matrix class I've already implemented. Matrix<float> mat(30, 30); for(size_t row = 0; row < mat.rows(); row++) {//Assume Row-Major ordering for performance reasons for(...
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  • 483
1 vote
1 answer
1k views

Implementation of Matrix<T>: std::vector<T> vs std::unique_ptr<T[]>?

As part of a hobby project, I needed a rectangular Matrix object to maintain state of a grid. At first, the implementation seemed trivial and unworthy of further discussion: (I haven't included all ...
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  • 483
-1 votes
1 answer
128 views

Aligning text columns of different size and content

In a past posting, I asked about commands in Bash to align text columns against one another by row. It has become clear to me that the desired task (i.e., aligning text columns of different size and ...
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3 votes
3 answers
112 views

Say we have a group of N person, and each person might want to sell or buy one of the M items, how to find a closed path among them for an exchange?

Say we have N persons and M items (when a person has a certain item, she usually only has one piece). For example, person 1 has item A, C, D, and wants item F person 2 has item B, C, and wants E ...
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  • 141
-1 votes
1 answer
184 views

Rotate a matrix in place, moving elements? (How to write a part of flow/logic after understanding the problem?)

Following is a java solution of the classic question of rotating a nxn matrix in place clockwise by 90 degrees. public void rotate(int[][] matrix, int n) { for (int layer = 0; layer < n / 2; ++...
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  • 113
0 votes
1 answer
433 views

Algorithm to find the highest Tetromino in a Tetris board?

Lets say that our Tetris board is represented as a 2D array of zeros and ones, where a 0 means empty and 1 means occupied, and you where asked to find the highest row in which a tetromino exists. ...
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1 vote
2 answers
185 views

Place X items in N matrices without repeat column and row

I have N matrices (n × m) and items to place in each one (n · m). The same items are repeated randomly for each matrix. When one item is placed in (i, j), for the following matrices the ...
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8 votes
5 answers
9k views

Which algorithm is performant for matrix multiplication of 4x4 matrices of affine transformations

I am wondering what is a good, performant algorithm for matrix multiplication of 4x4 matrices. I am implementing some affine transformations and I am aware that there are several algorithms for ...
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  • 2,988
19 votes
2 answers
5k views

How did Strassen come up with his matrix multiplication method?

The famous Strassen's matrix multiplication algorithm is a real treat for us, as it reduces the time complexity from the traditional O(n3) to O(n2.8). But of all the resources I have gone through, ...
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