leetcode 867. Transpose Matrix

class Solution {
public:
    vector<vector<int>> transpose(vector<vector<int>>& A) {
        vector<vector<int>> res;
        int m = A.size();
        int n = A[0].size();
        vector<int> c;
        for (int i=0;i<n;i++)
        {
            
            for (int j = 0;j<m;j++)
            {
                c.push_back(A[j][i]);
             }
            res.push_back(c);
            c.clear();
         }
        return res;
    }
};