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 one-dimensional 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. --- I understand it is C++ specific (according to the description), but it is general programming problem. Thanks
