如何在c++中垂直打印出二维矢量的元素？

#include <iostream>
#include <vector>

void printVerticalVector(const std::vector<std::vector<int>>& matrix) {
    int rows = matrix.size();
    int cols = matrix[0].size();

    for (int j = 0; j < cols; j++) {
        for (int i = 0; i < rows; i++) {
            std::cout << matrix[i][j] << std::endl;
        }
    }
}

int main() {
    std::vector<std::vector<int>> matrix = {{1, 2, 3},
                                            {4, 5, 6},
                                            {7, 8, 9}};

    printVerticalVector(matrix);

    return 0;
}

1
4
7
2
5
8
3
6
9