
Matrix Transpose
Code:
I store matrix entries in std::vector<double>, such that the reading is row by row.
This means, for matrix
1 3 4 8 9 3
3 6 8 1 1 2
2 0 9 8 7 6
the std::vector<double> would have entries: {1,3,4,8,9,3,3,6,8,1,1,2,2,0,9,8,7,6}.
To transpose the matrix I use the naive approach of iterating through std::vector, calculating for each
entry its position in a matrix transpose. Recently, I got one suggestion:
"When you have a matrix and a mapping to a onedimensional vector, transposing is equivalent to a permutation. Now execute this permutation by sorting the elements by requested rank in the permutation result."
I understand that transposing is equivalent to a permutation, but I dont know how to approach the problem this way.
Any suggestion on how to do this (or to do matrix transpose is a faster way) is welcome.


Whats wrong with the way you did it to start with? I dont quite get what the issue you are having is? apart from curiosity to know if there is a superfix in a library to do this for you? all i would do is use operations on rows and columns integers to reorder the linear array as required, i dont know if there is anything in the stl that does this for you but if so go look it up.