leetcode-48 Rotate Image

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You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Given input matrix = 
[
  [1,2,3],
  [4,5,6],
  [7,8,9]
],

rotate the input matrix in-place such that it becomes:
[
  [7,4,1],
  [8,5,2],
  [9,6,3]
]

Example 2:

Given input matrix =
[
  [ 5, 1, 9,11],
  [ 2, 4, 8,10],
  [13, 3, 6, 7],
  [15,14,12,16]
], 

rotate the input matrix in-place such that it becomes:
[
  [15,13, 2, 5],
  [14, 3, 4, 1],
  [12, 6, 8, 9],
  [16, 7,10,11]
]

选择二维数组，并只能在原先的数组上进行变化：解题思路 从某个点开始 对其影响的范围内数据都进行变动。

1  2  3           7   2     1            7    4    1

4  5  6   -》   4    5   6   -》    8      5     2 

7  8  9           9     8    3          9       6      3 

实现方法如下：

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

    public void rotate(int[][] matrix,int before,int i,int j,int beforeI,int beforeJ) {
        if(i  == beforeI && j == beforeJ) {
            return;
        }
        int temp = matrix[i][j];
        matrix[i][j] = before;
        rotate(matrix,temp,j,matrix.length-1-i,beforeI,beforeJ);
    }