package main

/**
 * '1' 2 '3'  swap   '7' 2 '1'  next   7 '2' 1
 *  4  5  6  ----->   4  5  6  -----> '4' 5 '6' -> ...
 * '7' 8 '9'         '9' 8 '3'         9 '8' 3
 */
func rotate(matrix [][]int) {
	side := len(matrix) - 1
	for i := 0; i <= side/2; i++ {
		for j := 0; j < side-2*i; j++ {
			matrix[i][i+j], matrix[i+j][side-i], matrix[side-i][side-i-j], matrix[side-i-j][i] = matrix[side-i-j][i], matrix[i][i+j], matrix[i+j][side-i], matrix[side-i][side-i-j]
		}
	}
}

/* func main() {
	m1 := [][]int{
		{11, 22, 33, 44, 55},
		{16, 27, 38, 49, 50},
		{11, 23, 35, 47, 59},
		{12, 24, 36, 48, 50},
		{15, 24, 33, 42, 51},
	}
	rotate(m1)
	fmt.Println(m1)
	m2 := [][]int{
		{1, 2},
		{3, 4},
	}
	rotate(m2)
	fmt.Println(m2)
	m3 := [][]int{}
	rotate(m3)
	fmt.Println(m3)
} */