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?

 

 1 public class Solution {

 2     public void rotate(int[][] matrix) {

 3         // Note: The Solution object is instantiated only once and is reused by each test case.

 4         if(matrix == null || matrix.length == 0 || matrix[0].length == 0) return;

 5         int dep = 0;

 6         int len = matrix.length - 1;

 7         int start = 0;

 8         int end = matrix.length - 1;

 9         while(start <= end)

10         {

11             int cur = 0;

12             for(int i = start; i < end; i ++){

13                 cur = matrix[dep][i];

14                 matrix[dep][i] = matrix[len - i][dep];

15                 matrix[len - i][dep] = matrix[len - dep][len - i];

16                 matrix[len - dep][len - i] = matrix[i][len - dep];

17                 matrix[i][len - dep] = cur;

18             }

19             start ++;

20             end --;

21             dep += 1;

22         }

23     }

24 }

 第三遍：

 1 public class Solution {

 2     public void rotate(int[][] matrix) {

 3         if(matrix == null || matrix.length == 0 || matrix[0].length == 0) return;

 4         int top = 0, bot = matrix.length - 1, len = matrix.length - 1;

 5         while(top < bot){

 6             for(int i = top; i < bot; i ++){

 7                 int tmp = matrix[top][i];

 8                 matrix[top][i] = matrix[len - i][top];

 9                 matrix[len - i][top] = matrix[bot][len - i];

10                 matrix[bot][len - i] = matrix[i][bot];

11                 matrix[i][bot] = tmp;

12             }

13             top ++;  bot --; 

14         }

15     }

16 }