rotate image

class Solution {
public:
    void rotate(vector<vector<int> > &matrix) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if( matrix.size() == 1 ) return;
        int start = 0;
        int n = matrix.size();
        int tmp = 0;
        while( start < n )
        {
            for(int i=start;i<n-1;i++)
            {
               
                tmp = matrix[start][i];
                matrix[start][i] = matrix[n-1-(i-start)][start];
                
                matrix[n-1-(i-start)][start]= matrix[n-1][n-1-(i-start)];
                matrix[n-1][n-1-(i-start)] = matrix[i][n-1];
                matrix[i][n-1] = tmp;
            }
           
            start ++;
            n --;
        }
        return;
        
    }

};