867

867. Transpose Matrix (Easy)

Given a 2D integer array matrix, return the transpose of matrix.

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

 

Example 1:

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

Example 2:

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

 

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= m, n <= 1000
• 1 <= m * n <= 105
• -109 <= matrix[i][j] <= 109

Companies: Amazon, Bloomberg, Apple, Citadel

Related Topics:
Array, Matrix, Simulation

Hints:

• We don't need any special algorithms to do this. You just need to know what the transpose of a matrix looks like. Rows become columns and vice versa!

Solution 1.

// OJ: https://leetcode.com/problems/transpose-matrix/
// Author: github.com/lzl124631x
// Time: O(MN)
// Space: O(1) extra space
class Solution {
public:
    vector<vector<int>> transpose(vector<vector<int>>& A) {
        int M = A.size(), N = A[0].size();
        vector<vector<int>> ans(N, vector<int>(M));
        for (int i = 0; i < M; ++i) {
            for (int j = 0; j < N; ++j) {
                ans[j][i] = A[i][j];
            }
        }
        return ans;
    }
};