【笔记】和算法无关的那些东东

可变参数函数

以不定参数求和为例

#include<bits/stdc++.h>
using namespace std;
int sum2(initializer_list<int>il){
    int sum=0;
    for(auto it=il.begin();it!=il.end();it++){
    sum += *it;
    }
    return sum;
}
int sum(int count,...){
    va_list ap;
    va_start(ap,count);
    int sum=0;
    for(int i=0;i<count;i++){
    sum+=va_arg(ap,int);
    }
    va_end(ap);
    return sum;
}

int main(){
    cout<<sum(3,1,2,5)<<endl;
    cout<<sum2({1,2,5})<<endl;
}

分数类

struct Rat {
  LL a, b;
  Rat(LL a=0):a(a),b(1) { }
  Rat(LL x, LL y):a(x),b(y) {
    if(b < 0) a = -a, b = -b;
    LL d = __gcd(a, b); if(d < 0) d = -d;
    a /= d; b /= d;
  }
};

 Int128

struct Int_128{
    unsigned long long a,b;
    Int_128(ll x){a=0,b=x;}
    friend bool operator < (Int_128 x,Int_128 y)
    {
        return x.a<y.a||x.a==y.a&&x.b<y.b;
    }
    friend Int_128 operator + (Int_128 x,Int_128 y)
    {
        Int_128 re(0);
        re.a=x.a+y.a+(x.b+y.b<x.b);
        re.b=x.b+y.b;
        return re;
    }
    friend Int_128 operator - (Int_128 x,Int_128 y)
    {
        y.a=~y.a;y.b=~y.b;
        return x+y+1;
    }
    void Div2()
    {
        b>>=1;b|=(a&1ll)<<63;a>>=1;
    }
    friend Int_128 operator * (Int_128 x,Int_128 y)
    {
        Int_128 re=0;
        while(y.a||y.b)
        {
            if(y.b&1)re=re+x;
            x=x+x;y.Div2();
        }
        return re;
    }
    friend Int_128 operator % (Int_128 x,Int_128 y)
    {
        Int_128 temp=y;
        int cnt=0;
        while(temp<x)temp=temp+temp,++cnt;
        for(;cnt>=0;cnt--)
        {
            if(temp<x)x=x-temp;
            temp.Div2();
        }
        return x;
    }
};