# Rotate Image Leetcode

#1

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]
]
```

#2

The below algorithm first swaps the last and first rows and then swap the indexes at `i, j` with `j, i`.

``````class Solution {
public void rotate(int[][] matrix) {
if(matrix==null) return;
int m = matrix.length, n = matrix[0].length;
for(int i=0, j=m-1;i<j;i++, j--){
int[] temp = matrix[i];
matrix[i] = matrix[j];
matrix[j] = temp;
}

for(int i=0;i<m;i++){
for(int j=i+1;j<n;j++){
int temp = matrix[i][j];
matrix[i][j] = matrix[j][i];
matrix[j][i] = temp;
}
}
}
}
``````