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### Decompose Commutators

A theorem in this paper1 states that every integral n-by-n matrix M over the integers with trace M = 0 is a commutator, that means there are two integral matrices A,B of the same size ...
6answers
974 views

### Subtract the Folded Matrix

Challenge: Given an NxN matrix where $N\geq2$ and one of eight distinct 'folding options', output a 2D array/list with the subtracted values. The eight folding options are: left-to-right; right-to-...
15answers
3k views

### Matrix Jigsaw Puzzles

Input: An integer n Two equal-sized square matrices (with their width/height being a multiple of n) Output: One of two ...
7answers
647 views

### Whose neighbours are hostile?

Introduction For the purposes of this challenge, we will define the neighbours of an element $E$ in a square matrix $A$ (such that $E=A_{i,j}$) as all the entries of $A$ that are immediately ...
8answers
654 views

### Classify a region by its slope

Definitions The kth ring of a square matrix of size N, where 1 ≤ k ≤ ceiling(N/2) is the list formed by the elements of the kth and (N-k+1)th rows and columns, but without the first and last k-1 ...
20answers
1k views

### Compute the Optimal Square Matrix

The optimal matrix (for the rather narrow scope of this challenge) is obtained by "zipping" the elements from the corresponding rows and columns of a square matrix and getting the maximum of each pair....
21answers
1k views

### Sum the deltas of my matrix

Background The deltas of an array of integers is the array formed by getting the differences of consecutive elements. For example, [1, 2, 4, 7, 3, 9, 6] has the ...
18answers
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-...