Inspired by Raymond Chen\'s post, say you have a 4x4 two dimensional array, write a function that rotates it 90 degrees. Raymond links to a solution in pseudo code, but I\'d
Here is the Java version:
public static void rightRotate(int[][] matrix, int n) {
    for (int layer = 0; layer < n / 2; layer++) {
        int first = layer;
        int last = n - 1 - first;
        for (int i = first; i < last; i++) {
           int offset = i - first;
           int temp = matrix[first][i];
           matrix[first][i] = matrix[last-offset][first];
           matrix[last-offset][first] = matrix[last][last-offset];
           matrix[last][last-offset] = matrix[i][last];
           matrix[i][last] = temp;
        }
    }
}
the method first rotate the mostouter layer, then move to the inner layer squentially.