(Java)LeetCode-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?

这道题木有什么难度，原地顺时针旋转一个矩阵90度，要求时间复杂度O（n2），空间复杂度O(1)

两层循环，外层循环每循环一次旋转“一层”，逐步向里旋转。就酱，代码如下：

public class Solution {
    public void rotate(int[][] matrix) {
        int n = matrix.length;
		int temp = 0;
		for(int i = 0; i <= (n-1)/2 ; i++ ){
			for(int j = i ; j < n - 1 - i; j++){
				temp = matrix[i][j];
				matrix[i][j] = matrix[n-1-j][i];
				matrix[n-1-j][i] = matrix[n-1-i][n-1-j];
				matrix[n-1-i][n-1-j] = matrix[j][n-1-i];
				matrix[j][n-1-i] = temp;
			}
		}
    }
}