将元素添加到2D矢量(矢量的矢量) C++

#include <iostream>
#include <vector>

int main() {
    // 创建一个二维矢量
    std::vector<std::vector<int>> matrix;

    // 添加元素到二维矢量
    std::vector<int> row1 = {1, 2, 3};
    std::vector<int> row2 = {4, 5, 6};
    std::vector<int> row3 = {7, 8, 9};

    matrix.push_back(row1);
    matrix.push_back(row2);
    matrix.push_back(row3);

    // 打印二维矢量
    for (const auto& row : matrix) {
        for (const auto& element : row) {
            std::cout << element << " ";
        }
        std::cout << std::endl;
    }

    return 0;
}