Leetcode: Rotate Image (4ms)

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

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

Analysis:

Rotate through triangle first (slash direction) and then rotate through middle of row. 

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//code 4ms

class Solution {

public:

    void rotate(vector<vector<int>>& matrix) {

        int n = matrix.size();

        for(int i=0;i<n;i++){

            for(int j=0;j<n-i-1;j++){

                swap(matrix[i][j],matrix[n-j-1][n-i-1]);//rotate through diagonal  

            }

        }

        for(int i=0;i<n/2;i++){

            for(int j=0;j<n;j++){

                swap(matrix[i][j],matrix[n-i-1][j]);//rotate through middle of row

            }

        }

    }

};