### LeetCode Challenge #48. Rotate Image

You are given an `n x n` 2D `matrix` representing an image, rotate the image by 90 degrees (clockwise).

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:

```Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]
```

Example 2:

```Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
```

Constraints:

• `n == matrix.length == matrix[i].length`
• `1 <= n <= 20`
• `-1000 <= matrix[i][j] <= 1000`
##### Video Solution
###### Java Solution
```				```
class Solution {
public void rotate(int[][] matrix) {
int n = matrix.length;
for(int i=0;i<n;i++){
for(int j=i;j<n;j++){
int k = matrix[i][j];
matrix[i][j] = matrix[j][i];
matrix[j][i] = k ;
}
}

for(int i=0;i<matrix.length;i++){
int[] tempArr = matrix[i];
reverse(tempArr);
}
return ;
}

public void reverse(int[] arr ){
int start = 0 ;
int end = arr.length-1 ;
while(start<=end){
int k = arr[start];
arr[start] = arr[end];
arr[end] = k ;

start++ ;
end--;
}
}
}
```
```