解题方法

使用结构体存储数据，重写std::cin和std::cout并使用std::sort来完成题目要求。

C++代码

#include <iostream>
#include <iomanip> // std::setprecision()
#include <string>
#include <algorithm>

struct tuple
{
    int x;
    float y;
    std::string z;

    tuple(int x, float y, std::string z)
        : x(x), y(y), z(z)
    {}

    tuple()
        :x(0), y(0.0),z("")
    {}

    friend std::istream& operator>>(std::istream& is, tuple& t);
    friend std::ostream& operator<<(std::ostream& output, const tuple& t);

};

std::istream& operator>>(std::istream& input, tuple& t)
{
    input >> t.x >> t.y >> t.z;
    return input;
}

std::ostream& operator<<(std::ostream& output, const tuple& t)
{
    output << t.x << " " << std::fixed << std::setprecision(2) << t.y << " " << t.z;
    return output;
}

int main()
{
    int cnt = 0;
    std::cin >> cnt;
    tuple* tps = new tuple[cnt];
    for (int i = 0; i < cnt; i++)
        std::cin >> tps[i];
    std::sort(tps, tps + cnt, [](const tuple& lhs, const tuple& rhs) { return lhs.x < rhs.x; });
    for (int i = 0; i < cnt; i++)
        std::cout << tps[i] << "\n";

    delete[] tps;
}