Problem 1972. Convert matrix to 3D array of triangular matrices
Given a 2D numeric array x in which each column represents the vectorized form of an upper triangular matrix, return a 3D array y containing the concatenated triangular matrices.
- If the size of the input matrix x is MxN, then the size of the output matrix y is PxPxN, where M = sum(1:P)
- You may assume that P<=100
Example
If
x = 1 7 13 2 8 14 3 9 15 4 10 16 5 11 17 6 12 18
then
y(:,:,1) = 1 2 4 0 3 5 0 0 6
y(:,:,2) = 7 8 10 0 9 11 0 0 12
y(:,:,3) = 13 14 16 0 15 17 0 0 18
NOTE: If you are wondering why this seems like a strange task, it is inspired by a genotype->phenotype mapping I am doing in a genetic algorithm.
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