[LeetCode] Transpose Matrix 转置矩阵

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. 1 <= A.length <= 1000
2. 1 <= A[0].length <= 1000

这道题让我们转置一个矩阵，所谓矩阵的转置，就是把 mxn 的矩阵变为 nxm 的，并且原本在 A[i][j] 位置的数字变到 A[j][i] 上即可，非常的简单直接。我们新建一个 nxm 的矩阵，然后遍历原矩阵中的每个数，将他们赋值到新矩阵中对应的位置上即可，参见代码如下：

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

参考资料：

https://leetcode.com/problems/transpose-matrix/

https://leetcode.com/problems/transpose-matrix/discuss/146797/C%2B%2BJavaPython-Easy-Understood

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