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Q187FreeSystemVerilog

Transpose a square matrix in place

Difficulty
Easy
Topic
Matrices
Language
SV
Interview prompt

Question

Transpose an N x N matrix in place.

Symbolic four-by-four matrix with its main diagonal and three mirrored off-diagonal cell pairs
An in-place transpose swaps each mirrored off-diagonal pair once while leaving the diagonal unchanged.
Candidate starting point

Implementation scaffold

typedef int int_matrix_t[][];

function automatic void transpose_square(ref int_matrix_t matrix);
  // TODO: implement.
endfunction
Reviewed example

Trace one case

Input
matrix = [[1, 2], [3, 4]]
Expected output
[[1, 3], [2, 4]]

Swapping the off-diagonal pair performs the square transpose in place.

What to cover

Requirements

  1. Assume the input has N rows and every row has exactly N elements.
  2. Swap only one side of the diagonal.
  3. Leave diagonal elements unchanged.
  4. Use O(1) extra space.
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