Rotate Image

Problem Statement - link #

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.

Examples #

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

Solutions #

class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        int n = size(matrix);
        reverse(begin(matrix),end(matrix));
        for(int i=0;i<n;i++)
            for(int j=0;j<i;j++)
                swap(matrix[i][j],matrix[j][i]);
        return;
    }
};