Question

Inspired by Raymond Chen’s post, say you have a 4×4 two dimensional array, write a function that rotates it 90 degrees. Raymond links to a solution in pseudo code, but I’d like to see some real world stuff.

[1][2][3][4] [5][6][7][8] [9][0][1][2] [3][4][5][6] 

Becomes:

[3][9][5][1] [4][0][6][2] [5][1][7][3] [6][2][8][4] 

Update: Nick’s answer is the most straightforward, but is there a way to do it better than n^2? What if the matrix was 10000×10000?

Answer 1

Here it is in C#

int[,] array = new int[4,4] {     { 1,2,3,4 },     { 5,6,7,8 },     { 9,0,1,2 },     { 3,4,5,6 } };  int[,] rotated = RotateMatrix(array, 4);  static int[,] RotateMatrix(int[,] matrix, int n) {     int[,] ret = new int[n, n];      for (int i = 0; i < n; ++i) {         for (int j = 0; j < n; ++j) {             ret[i, j] = matrix[n - j - 1, i];         }     }      return ret; }