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Questions tagged [matrix]

A matrix is a list of numbers arranged in a rectangle with rows and columns. In programming, it is also known as a 2D array. Use this tag if your challenge is about manipulating matrices.

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Calculate the permanent as quickly as possible

The challenge is to write the fastest code possible for computing the permanent of a matrix. The permanent of an n-by-n matrix ...
3k views

Codegolf the permanent

The challenge is to write codegolf for the permanent of a matrix. The permanent of an n-by-n matrix ...
502 views

Image Smoothie!

Input into your program a black and white image. (png, jpg, etc) Convert the image to a 2D matrix of pixels, where each index is the grayscale value of the image. Take each index of the matrix and ...
429 views

Fill in the grid randomly

Given positive integer n < 10, create a 2 dimensional matrix where each location is filled with its x and ...
360 views

Generate binary matrices which are distinct up to reflections

Here are all the 2x2 binary matrices ...
2k views

Create a pyramidal matrix

A pyramidal matrix is a square matrix where all numbers increase or decrease from the center point, like the two matrices below: ...
5k views

Dijkstra's Challenge

Presented in honor of APL as an interactive tool turning 50 this year Background Ken [Iverson] presented his paper Formalism in Programming Languages in August 1963 at a Working Conference on ...
415 views

Index sum and strip my matrix

Index sum and strip my matrix Given a matrix/2d array in your preferable language Input: The matrix will always have an odd length The matrix will always be perfectly square The matrix values can ...
781 views

Alternating sign matrix verification

An alternating sign matrix is an n by n matrix consisting of the numbers -1, 0, 1, such that: The sum of each row and column is ...
368 views

Dot Product of Diagonals

This challenge is very simple. You are given as input a square matrix, represented in any sane way, and you have to output the dot product of the diagonals of the matrix. The diagonals in specific ...
826 views

Jordan Decomposition

Important note: Because this challenge only applies to square matrices, any time I use the term "matrix", it is assumed that I am referring to a square matrix. I am leaving off the "square" ...
1k views

Matrix Trigonometry

Introduction The two most common trigonometric functions, sine and cosine (or sin and ...
1k views

Calculate the Kronecker Product

Related, but very different. In the examples below, A and B will be 2-by-2 matrices, and the matrices are one-indexed. A ...
694 views

Find the Matrix Power

Problem Create a program or function that can calculate the result of a matrix raised to the nth power. Your code will take an arbitrary square matrix A and a non-negative integer n, and return a ...
845 views

Transform a matrix

Write a program or function where a matrix A (maximum value of dimensions of the matrix is 100) is transformed to a new matrix B. Each element of the new matrix B is the sum of the positive neighbors ...
674 views

Calculate the Kronecker sum of two matrices

In the examples below, A and B will be 2-by-2 matrices, and the matrices are one-indexed. A Kronecker product has the ...
170 views

Find the last position in a matrix walking like a spiral [closed]

This question will be deleted soon, do not read/answer it Introduction Given one matrix A x A and a number of movements N. ...
2k views

Diamondize a Matrix

Given a matrix, output a representation of the matrix where the top left element is on top, the anti-diagonal is the central row and the bottom right element is at the bottom. For example, consider ...
1k views

Sorting rectangular matrices

Given a matrix A, we can say that it is "sorted" if each row and column of A is sorted (ascending left-to-right for rows and top-...
765 views

Hilbert-Curvify a Matrix

Inspired by this question Another way to unroll a 2D image into a 1D string is to use an Hilbert Curve. There are many version of this curve, depending on the number of iterations used while ...
667 views

Reconstruct a zigzagified matrix

As part of its compression algorithm, the JPEG standard unrolls a matrix into a vector along antidiagonals of alternating direction: Your task is to take the unrolled vector along with the matrix ...
4k views

Zigzagify a Matrix

As part of its compression algorithm, the JPEG standard unrolls a matrix into a vector along antidiagonals of alternating direction: Your task is to take a matrix (not necessarily square) and return ...
988 views

Is this a submatrix?

This is the 2-dimensional generalisation of this challenge. For our purposes, one matrix (or 2D array) A is considered a submatrix of another matrix B, if A can be obtained by completely removing a ...
606 views

Rotate every 2x2 block in a matrix

The Challenge Given a n x m matrix with n > 1 and m > 1 filled with integers 1 2 3 ...
568 views

Rotate every row and column in a matrix

The Challenge Given a n x n matrix of integers with n >= 2 1 2 3 4 and a list of integers with exactly ...
981 views

Vandermonde Determinant

Given a vector of n values (x1,x2,x3,...,xn) return the determinant of the corresponding Vandermonde matrix. This determinant ...
1k views

Recursive 2x2 determinant

The determinant of a 2 by 2 matrix a b c d is given by ad - bc. Given a matrix of digits with dimensions 2n by 2n, n ≥ 1, ...
1k views

Fibonacci-style matrix expansion

For each row and then column of a matrix, we can add an extra entry with the sum of the last two entries in that row or column. For example with the following input matrix: ...
5k views

Construct the Identity Matrix

The challenge is very simple. Given an integer input n, output the n x n identity matrix. The identity matrix is one that has <...
640 views

Cofactor Matrices

The cofactor matrix is the transpose of the Adjugate Matrix. The elements of this matrix are the cofactors of the original matrix. The cofactor (i.e. the element of the cofactor matrix at row i and ...
667 views

Construct a companion matrix

You have a number of polynomials who are lonely, so make them some companions (who won’t threaten to stab)! For a polynomial of degree n, there is an ...
1k views

Reduced Row-Echelon Form of a Matrix

The goal of this challenge is to create a program that takes in a matrix and outputs its reduced row-echelon form. A matrix is in reduced row-echelon form if it meets all of the following ...
454 views

Multiply Pauli Matrices

The Pauli matrices are a set of 2x2 matrices which appear very commonly in quantum physics (no, you don't need to know any quantum physics for this challenge). If we include the identity in the set, ...
463 views

Find the inverse of a matrix

Write a full program to calculate the inverse of a 4-by-4 matrix. Rules The sixteen values of the initial matrix must be hard-coded to variables, as follows: ...
1k views

Solve a 2x2 Eigensystem

For those with a little linear algebra background, the challenge is as simple as this: determine the eigenvalues and eigenvectors of a given complex 2x2 matrix. You may skip ahead to The Challenge for ...