class Solution {
public:
vector<vector<int>> transpose(vector<vector<int>>& matrix) {
int n = matrix.size();
int m = matrix[0].size();
// 转置后的矩阵是m行n列
vector<vector<int>> res(m, vector<int>(n));
for (int i = 0; i < n; ++ i)
for (int j = 0; j < m; ++ j)
res[j][i] = matrix[i][j];
return res;
}
};