Spin Rings

• Time : O(nm)
• Space : O(1)

void spinRings(vector<vector<int>> &array, int start = 0) {
    int n = array.size(), m = array[0].size();
    if(min(n,m) / 2 == start) return;
    int sy = start, ey = n - start - 1, sx = start, ex = m - start - 1;
    int tmp = array[start][start];
    for(int i = sy; i < ey; i++) {
        array[i][sx] = array[i+1][sx];
    }
    for(int i = sx; i < ex; i++) {
        array[ey][i] = array[ey][i+1];
    }
    for(int i = ey; i > sy; i--) {
        array[i][ex] = array[i-1][ex];
    }
    for(int i = ex; i > sx; i--) {
        array[sy][i] = array[sy][i-1];
    }
    array[sy][sx+1] = tmp;

    spinRings(array, start + 1);
}