How to rotate a N x N matrix by 90 degrees? [closed]

Question

How to rotate a N x N matrix by 90 degrees. I want it to be inplace?

Answer 1

for(int i=0; i<n/2; i++)    for(int j=0; j<(n+1)/2; j++)        cyclic_roll(m[i][j], m[n-1-j][i], m[n-1-i][n-1-j], m[j][n-1-i]);   void cyclic_roll(int &a, int &b, int &c, int &d) {    int temp = a;    a = b;    b = c;    c = d;    d = temp; } 

Note I haven't tested this, just compoosed now on the spot. Please test before doing anything with it.

Answer 2

here is my solution: (rotate pi/2 clockwise)

1. do the transpose of the array, (like matrix transpose)

2. reverse the elements for each row

   cons int row = 10; cons int col = 10; //transpose for(int r = 0; r < row; r++) {   for(int c = r; c < col; c++) {       swap(Array[r][c], Array[c][r]);   } } //reverse elements on row order for(int r = 0; r < row; r++) {     for(int c =0; c < col/2; c++) {       swap(Array[r][c], Array[r][col-c-1])     } } 

if rotate pi/2 in counter-clockwise

1. transpose the array

2. reverse the elements on column order

never test the code! any suggestion would be appreciated!