Questions tagged [matrix]
This tag is for challenges involving matrices. A matrix, also known as a 2D array, is a list of numbers arranged in a rectangle with rows and columns.
303 questions
Score of 11
17 answers
627 views
Hodge star operator for three-dimensional 1-forms
Objective
Given a three-dimensional vector:
$$
\mathbf{v} = \begin{bmatrix}
a \\
b \\
c
\end{bmatrix}
$$
Output the following matrix:
$$
\star\mathbf{v} = \begin{bmatrix}
0 & c & -b \\
-c &...
- reputation score 7933
Score of 12
7 answers
2451 views
Do Not Find the Fox in all possible ways
Do Not Find the Fox is a non-game where you repeat the following up to 16 times:
Pick an empty square in a 4×4 grid
Draw a tile from a bag – there are 5 Fs, 6 Os and 5 Xs at first – and place it in ...
- reputation score 4759
Score of 23
11 answers
3986 views
Is it France, Netherlands or Poland?
Below are simplified versions of the flags of France, Netherlands and Poland respectively, as 9x6 pixels:
See here for a plain text version.
(Many other flags use this color scheme, but I think a ...
- reputation score 207890
Score of 2
4 answers
327 views
Find the busiest unfriendly matrix
This is about \$n\$ by \$n\$ binary matrices. Call a pair of rows unfriendly if the Hamming distance between the two rows is larger than the number ones they have in common positions. Let us call a ...
- reputation score 3197
Score of 3
4 answers
660 views
Create 251610 matrices as quickly as possible
There are 251610 6 by 6 binary matrices that are inequivalent. We say two matrices are equivalent if there is some permutation of their rows and/or columns that makes them equal.
For example:
...
- reputation score 3197
Score of 15
19 answers
2680 views
Is this a Hadamard matrix?
Hadamard matrices is a square matrix whose entries are either +1 or −1 and whose rows are mutually orthogonal.
In other words, it means that each pair of rows has matching entries in exactly half of ...
- reputation score 5205
Score of 12
6 answers
1788 views
9-16-25 2D Matrix
Given three grids and the sum of rows and columns of each grid, your task is:
Grid \$3×3\$: Fill the grid from \$1\$ to \$9\$, ensure no repeats within the grid.
Grid \$4×4\$: Fill the grid from \$1\...
user123147
Score of 12
7 answers
1592 views
Contract a tensor
Introduction
Tensor contraction is an operation that can be performed on a tensor. It is a generalization of the idea of the trace of a matrix. For example, if we have a rank-2 tensor (a matrix) and ...
- reputation score 3205
Score of 4
1 answer
716 views
Which line is best?
Consider an \$n \times n\$ grid of integers. The task is to draw a straight line across the grid so that the part that includes the top left corner sums to the largest number possible. Here is a ...
- reputation score 3197
Score of 9
5 answers
1203 views
Compute the logarithm of a matrix
There have already been challenges about computing the exponential of a matrix , as well as computing the natural logarithm
of a number. This challenge is about finding the (natural) logarithm of ...
- reputation score 6135
Score of 17
22 answers
2152 views
Compute this fractal matrix
The unique-disjointness matrix ( UDISJ(n) ) is a matrix on all pairs of subsets of {1...,n} with entries $$ U_{(A,B)}=\begin{cases}
0, ~ if ~ |A\cap B|=1\\
1, ~ ...
- reputation score 6135
Score of 27
42 answers
2429 views
Diagonalize a vector
Diagonalize a vector into a matrix.
Input
A vector, list, array, etc. of integers \$\mathbf{v}\$ of length \$n\$.
Output
A \$n \times n\$ matrix, 2D array, etc. \$A\$ such that for each element \$a_i \...
- reputation score 11554
Score of 1
0 answers
142 views
Bunny Shakespeare poetry [closed]
Suppose you have a grid of cells that is 6 wide and arbitrarily tall. In each cell is a word. Let the bottom row, which is row #1, be the last 6 words of sample.txt in order. Let the second to last ...
- reputation score 121
Score of 1
0 answers
143 views
Print all semimagic squares [closed]
I am working on a code to print all semimagic squares [1] of a given size. I am working with the following definition:
An \$n\times n\$ consists of numbers \$1,2,\cdots, n^2\$.
All numbers must be ...
- reputation score 111
Score of 24
29 answers
2261 views
Borders of a Rectangular Matrix
Although it's done a few times as sub-challenge of a larger challenge, and we also have a challenge to remove the borders of a square matrix, I couldn't find a challenge to output the borders of a ...
- reputation score 137619
