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?

public class Solution {
    public void rotate(int[][] matrix) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(matrix == null || matrix.length == 0 || matrix[0].length == 0) return;
        int dep = 0;
        int len = matrix.length - 1;
        int start = 0;
        int end = matrix.length - 1;
        while(start <= end)
        {
            int cur = 0;
            for(int i = start; i < end; i ++){
                cur = matrix[dep][i];
                matrix[dep][i] = matrix[len - i][dep];
                matrix[len - i][dep] = matrix[len - dep][len - i];
                matrix[len - dep][len - i] = matrix[i][len - dep];
                matrix[i][len - dep] = cur;
            }
            start ++;
            end --;
            dep += 1;
        }
    }
}

 第三遍：

public class Solution {
    public void rotate(int[][] matrix) {
        if(matrix == null || matrix.length == 0 || matrix[0].length == 0) return;
        int top = 0, bot = matrix.length - 1, len = matrix.length - 1;
        while(top < bot){
            for(int i = top; i < bot; i ++){
                int tmp = matrix[top][i];
                matrix[top][i] = matrix[len - i][top];
                matrix[len - i][top] = matrix[bot][len - i];
                matrix[bot][len - i] = matrix[i][bot];
                matrix[i][bot] = tmp;
            }
            top ++;  bot --; 
        }
    }
}