Rotate Image

问题描述

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?

 

解决思路

难点在于，如何原地进行旋转操作。

程序

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