简单分数的化简、四则运算、输出

int gcd(int a,int b){
    if(b==0) return a;
    return gcd(b,a%b);
}
struct Fraction{
    int up,down;
};

int gcd(int a,int b){
    if(b==0) return a;
    else return gcd(b,a%b);
}
//分数的化简
Fraction reduction(Fraction result){
    if(result.down<0){
        result.up=-result.up;
        result.down=-result.down;
    }
    if(result.up==0){
        result.down=1;
    }
    else{
        int d=gcd(result.down,result.up);
        result.down/=d;
        result.up/=d;
    }
}
Fraction add(Fraction f1,Fraction f2){
    Fraction result;
    result.up=f1.up*f2.down+f2.up*f1.down;
    result.down=f1.down*f2.down;
    return reduction(result);
}
Fraction minu(Fraction f1,Fraction f2){
    Fraction result;
    result.up=f1.up*f2.down-f2.up*f1.down;
    result.down=f1.down*f2.down;
    return reduction(result);
}
Fraction multi(Fraction f1,Fraction f2){
    Fraction result;
    result.up=f1.up*f2.up;
    result.down=f1.down*f2.down;
    return reduction(result);
}
Fraction divide(Fraction f1,Fraction f2){
    Fraction result;
    result.up=f1.up*f2.down;
    result.down=f1.down*f2.up;
    return reduction(result);
}
//先化简，可能有假分数、真分数、负分数
void showResult(Fraction r){
    r=reduction(r);
    if(r.down==1) printf("%d",r.up);
    else if(abs(r.up)>r.down){
        printf("%d %d/%d",r.up/r.down,abs(r.up)%r.down,r.down);
    }
    else{
        printf("%d/%d",r.up,r.down);
    }
}