leetcode 48 solution

 48. Rotate Image

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]]

 

Constraints:

• n == matrix.length == matrix[i].length
• 1 <= n <= 20
• -1000 <= matrix[i][j] <= 1000

solution:

class Solution {

public:

    void swap(int& a , int &b)

    {

        int c ;

        c = a;

        a = b;

        b = c;

    }

    void transpose (vector<vector<int>>& m)

    {

        int p = m.size();

        for(int i = 0 ; i < p ; i++)

        {

            for(int j =i+1 ; j < p ; j++)

            {

                swap(m[i][j] , m[j][i] );

            }

        }

    }

    void reverse_matrix(vector<vector<int>>&m )

    {   

        int k = m.size();

        for(int i = 0 ; i < k ; i++)

        {

            for(int j = 0 ; j < k/2 ; j++)

            {

                swap(m[i][j] , m[i][k-1-j]);

            }

        }

    }

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

    {

        

        transpose(matrix);

        int l = matrix.size();

        int i =0;

        reverse_matrix(matrix );

        

    }

};