import java.util.Arrays;

/**

 * You are given an n x n 2D matrix representing an image.

 Rotate the image by 90 degrees (clockwise).

 Follow up:

 Could you do this in-place?

翻转二维数组，思路是把数组分成length/2层，每层分别翻转，左边的到上边，下边的到左边，右边的到下边，上边的到右边

 每层也有一个循环，设置一个中间量，这层的数一个一个交换，注意每层循环的次数（就是这层每条边的数量-1）

 */

public class Q48RotateImage {

    public static void main(String[] args) {

        int[][] matrix = new int[][]{{1,2,3,4,5},{6,7,8,9,10},{11,12,13,14,15},{16,17,18,19,20},{21,22,23,24,25}};

        rotate(matrix);

        for (int[] num :

                matrix) {

            System.out.println(Arrays.toString(num));

        }

    }

    public static void rotate(int[][] matrix) {

        int temp;

        int l = matrix.length;

        for (int i = 0; i < l / 2; i++) {

            for (int j = 0; j < l-1-(2*i); j++) {

                temp = matrix[i][i+j];

                matrix[i][i+j] = matrix[l-1-i-j][i];

                matrix[l-1-i-j][i] = matrix[l-1-i][l-1-i-j];

                matrix[l-1-i][l-1-i-j] = matrix[i+j][l-1-i];

                matrix[i+j][l-1-i] = temp;

            }

        }

    }

}