P1458 顺序的分数 Ordered Fractions（有技巧的枚举）+C++类封装=精简代码

#include<bits/stdc++.h>
using namespace std;
struct Fract
{
    int n,d;
    bool operator < (const Fract & tmp){return n * tmp.d < tmp.n * d;}
    void print(){  cout << n << '/' << d<<endl;}
    Fract(int a,int b):n(a),d(b){}
};
int main()
{
    int n;
    vector<Fract> res;
    res.push_back(Fract(0, 1));
    cin >> n;
    for (int i = 2; i <= n; i++)
        for (int j = 1; j < i; j++)
            if (__gcd(j, i) == 1)     res.push_back(Fract(j, i ));
    res.push_back(Fract(1, 1 ));
    sort(res.begin(),res.end());
    for (auto i=res.begin();i!=res.end();i++)    i->print();
    return 0;
}