LeetCode(048) Rotate Image

题目如下：

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?



分析如下：

首先沿着对角线(左上->右下)方向翻折，然后沿着中轴方向翻折。

我的代码：

/*

[1][2]              [3][1]
[3][4]    ----->    [4][2]

[1][2]  沿对角线翻折  [1][3]    沿中轴翻折    [3][1]
[3][4]    ----->    [2][4]    ------>     [4][2]
*/
//257 ms
public class Solution {
    
    public void rotate(int[][] matrix) {
        
        for (int i = 0; i < matrix.length; ++i) {
            for (int j = i + 1; j < matrix[i].length; ++j) {
                int temp = matrix[i][j];
                 matrix[i][j] = matrix[j][i];
                 matrix[j][i] = temp;
            }
        }
        
        for (int i = 0; i < matrix.length; ++i) {
            for (int j = 0; j < matrix[i].length/2; ++j) {
                int temp = matrix[i][j];
                // BUG1 indexOutOfBound Exception
                //matrix[i][j] = matrix[i][matrix[i].length - j];
                //matrix[i][matrix[i].length - j] = temp;
                matrix[i][j] = matrix[i][matrix[i].length - j - 1];
                matrix[i][matrix[i].length - j - 1] = temp;
            }
        }
        
    }
}