This problem is related to the 17x17 challenge. See also Part 1 of this problem. Given a matrix in which each element is either 1, 2, 3, or 4, determine whether or not any rectangles are present. A rectangle is a formed whenever four instances of the same value appear in the corners of a rectangular region of the matrix.
Examples:
Input a = [ 4 1 2 4 1
3 3 2 1 4
3 2 4 1 1
1 4 3 2 2
1 1 1 4 4 ]
Output tf is false
You can't form any rectangles here.
Input a = [ 1 4 3 1
3 1 4 1
1 3 4 1
1 1 2 3 ]
Output tf is true
There is a rectangle: a([1 3],[1 4]) is [1 1; 1 1]
Solve

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Last Solution submitted on Mar 11, 2026

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