4
3

1
2
----------------------------------------------------
我的代码：

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

int gcd(int M, int N); // greatest common divisor of M and n ( M > N)

class Fraction{
    public:
    Fraction(int m, int n); // m/n
    //~Fraction();
    
    int getNumerator() const;
    int getDenominator() const;
    
    friend bool operator < (Fraction f1, Fraction f2);
    friend bool operator == (Fraction f1, Fraction f2);
    
    private:
    int numerator;
    int denominator;
    double value;
};

//////////////////////////////
Fraction::Fraction(int m, int n){
    int GreatestComDiv = gcd(n, m);
    if ( GreatestComDiv != 1){ //
        m /= GreatestComDiv;
        n /= GreatestComDiv;
    }
    numerator = m;
    denominator = n;
    value = (double)m/(double)n;
}

int Fraction::getNumerator() const{
    return numerator;
}

int Fraction::getDenominator() const{
    return denominator;
}
//////////////////////////////////////////
bool operator < (Fraction f1, Fraction f2){
    if (f1.value < f2.value){
        return true;
    }
    else{
        return false;
    }
}

bool operator == (Fraction f1, Fraction f2){
    if ((f1.numerator == f2.numerator) && (f1.denominator == f2.denominator)){
        return true;
    }
    else{
        return false;
    }
}
//////////////////////////////////////////////////
int main(int argc, char* argv[]){
    int n, orderOfFraction;
    cin>>n;
    cin>>orderOfFraction;
    
    vector<Fraction> fractions;
    typedef vector<Fraction>::size_type vec_sz;
    
    for (int i = n; i >= 2; --i){
        for (int j = i-1; j >= 1; --j){
            Fraction f(j, i);
            
            bool equal = false;
            vec_sz l = fractions.size();
            for (vec_sz k = 0; k < l; ++k){
                if (f == fractions[k]){
                    equal = true;
                }
            }
            
            if (!equal){
                fractions.push_back(f);
            }
        }
    }
    
    sort(fractions.begin(), fractions.end());
    
    cout<<fractions[orderOfFraction-1].getNumerator()<<endl;
    cout<<fractions[orderOfFraction-1].getDenominator()<<endl;
    
    return 0;
}

int gcd(int m, int n){
    while (n != 0){
        int r = m % n;
        m = n;
        n = r;
    }
    
    return m;
}