题解

#include<iostream>
#include<algorithm>
#include<map>
using namespace std;

int n;
map<double,string,less<double>> ha;
bool isvalid(int a,int b){
    return __gcd(a,b)==1 && a<=b && 1<=b && b<=n;
}
int main(){
    cin>>n;
    for (int i=0;i<=n;i++){
        for(int j=1;j<=n;j++){
            if (isvalid(i,j)){
                string str=to_string(i);
                str.push_back('/');
                str+=to_string(j);
                ha[i*1./j]=str;
            }
        }
    }
    for (auto pr:ha) cout<<pr.second<<endl;
    return 0;
}