如何在C++中对三元组进行排序？

#include<iostream>
#include<vector>
#include<algorithm>

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

    // 对三元组按第一个元素进行排序
    std::sort(triplets.begin(), triplets.end(), [](const std::tuple<int, int, int>& a, const std::tuple<int, int, int>& b) {
        return std::get<0>(a) < std::get<0>(b);
    });

    // 输出排序后的三元组
    for (const auto& t : triplets) {
        std::cout << "("<< std::get<0>(t) << ", "<< std::get<1>(t) << ", "<< std::get<2>(t) << ")"<< std::endl;
    }

    return 0;
}