# Leetcode 48. Rotate Image

###### tags: `Leetcode`

https://leetcode.com/problems/rotate-image/

## Description
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]]

**Example 3:**

Input: matrix = [[1]]
Output: [[1]]

**Example 4:**

Input: matrix = [[1,2],[3,4]]
Output: [[3,1],[4,2]]

**Constraints:**
- matrix.length == n
- matrix[i].length == n
- 1 <= n <= 20
- -1000 <= matrix[i][j] <= 1000

## Solution in C

Time Complexity: $O(n^2)$
Space Complexity: $O(1)$

void rotate(int** matrix, int matrixSize, int* matrixColSize){
    for(int i=0; i<(matrixSize+1)/2; i++){
        int k = matrixSize-i-1;
        for(int j=0; j<matrixSize/2; j++){
            int l = matrixSize-j-1;
            //rotate 90 degrees
            int temp = matrix[i][j];
            matrix[i][j] = matrix[l][i];
            matrix[l][i] = matrix[k][l];
            matrix[k][l] = matrix[j][k];
            matrix[j][k] = temp;
        }
    }
}