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

Rotate the image by 90 degrees (clockwise).

 

Example

Given a matrix

[    [1,2],    [3,4]]

rotate it by 90 degrees (clockwise), return

[    [3,1],    [4,2]]

Challenge

Do it in-place.

 

public class Solution {    /**     * @param matrix: A list of lists of integers     * @return: Void     */    public void rotate(int[][] matrix) {        // write your code here                if(matrix == null || matrix.length <= 1)            return;                int n = matrix.length;                for(int i = 0; i < n / 2; i++)            rotate(matrix, i);                return;    }        public void rotate(int[][] matrix, int num){                int n = matrix.length;                int start = num;        int end = n - 1 - num;                for(int i = 0; i < end - start; i++){            int temp = matrix[start][start + i];            matrix[start][start + i] = matrix[end - i][start];            matrix[end - i][start] = matrix[end][end - i];            matrix[end][end - i] = matrix[start + i][end];            matrix[start + i][end] = temp;        }                return;    }    }