leetcode-java-48. Rotate Image

/*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? *//*思路：本题要求不开辟新的空间，且矩阵行列相同其实就是1.先对角线做转置(左下到右上)2.在竖直中心轴对称交换 */ public class Solution {     public void rotate(int[][] matrix) {         int len = matrix.length;        //  先对角线做转置(左下到右上)         for(int i = 0;i < len;i++) {             for(int j = 0;j < i;j++) {                 int temp = matrix[i][j];                 matrix[i][j] = matrix[j][i];                 matrix[j][i] = temp;             }         }        //  在竖直中心轴对称交换        for(int i = 0;i < len;i++) {            for(int j = 0;j < len/2;j++) {                int temp = matrix[i][j];                matrix[i][j] = matrix[i][len-1-j];                matrix[i][len-1-j] = temp;            }        }     } }