867. Transpose Matrix.cpp

Given a matrix A, return the transpose of A.

The transpose of a matrix is the matrix flipped over it's main diagonal, switching the row and column indices of the matrix.





Example 1:

Input: [[1,2,3],[4,5,6],[7,8,9]]
Output: [[1,4,7],[2,5,8],[3,6,9]]
Example 2:

Input: [[1,2,3],[4,5,6]]
Output: [[1,4],[2,5],[3,6]]


Note:

1 <= A.length <= 1000
1 <= A[0].length <= 1000







class Solution {
public:
    vector<vector<int>> transpose(vector<vector<int>>& matrix) {
        int m=matrix.size();
        int n=matrix[0].size();
        vector<vector<int> > res(n, vector<int> (m, 0));  // res is n * m
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                res[i][j]=matrix[j][i];
            }
        }

        return res;
    }
};



//Alter
// If we have a N * N matrix, then, transpose can be found without extra space
/*
for(int i=0;i<n;i++){
    for(int j=i;j<n;j++){
        swap(mat[i][j], mat[j][i]);
    }
}
*/