如何复制二维字符串数组？

#include <iostream>
#include <string>

int main() {
    const int rows = 3;
    const int cols = 4;
    std::string arr[rows][cols] = {{"hello", "world", "this", "is", "a", "test"},
                                    {"hello", "world", "this", "is", "a", "test"},
                                    {"hello", "world", "this", "is", "a", "test"}};

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

    return 0;
}

#include <iostream>
#include <string>

std::vector<std::vector<std::string>> copy_2d_string_array(const std::vector<std::vector<std::string>>& arr) {
    std::vector<std::vector<std::string>> new_arr;
    new_arr.resize(arr.size());

    for (int i = 0; i < arr.size(); ++i) {
        new_arr[i].resize(arr[i].size());
        for (int j = 0; j < arr[i].size(); ++j) {
            new_arr[i][j] = arr[i][j];
        }
    }

    return new_arr;
}

int main() {
    const int rows = 3;
    const int cols = 4;
    std::vector<std::vector<std::string>> arr(rows, std::vector<std::string>(cols, ""));

    for (int i = 0; i < rows; ++i) {
        for (int j = 0; j < cols; ++j) {
            arr[i][j] = "hello world";
        }
    }

    std::vector<std::vector<std::string>> new_arr = copy_2d_string_array(arr);

    for (int i = 0; i < new_arr.size(); ++i) {
        for (int j = 0; j < new_arr[i].size(); ++j) {
            std::cout << new_arr[i][j] << " ";
        }
        std::cout << std::endl;
    }

    return 0;
}