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;
}
}
}
}