[模板] 高精度运算

使用vector作为基类，优点是空间动态分配，缺点是STL重度依赖，离开O2就很慢（除法未优化）

#include<algorithm>
#include<iostream>
#include<cstdio>
#include<vector>

using namespace std;

struct bign:vector<int>{
  bign(int n=0){
    push_back(n);
    check();
  }
  bign& check(){
    while(!empty()&&!back())pop_back();
    if(empty())return *this;
    for(unsigned int i=1;i<size();i++){
      (*this)[i]+=(*this)[i-1]/10;
      (*this)[i-1]%=10;
    }
    while(back()>=10){
      push_back(back()/10);
      (*this)[size()-2]%=10;
    }
    return *this;
  }
};
istream& operator>>(istream &is,bign &n){
  string s;is>>s;n.clear();
  for(int i=s.size()-1;i>=0;i--)n.push_back(s[i]-'0');
  return is;
}
ostream& operator<<(ostream &os,const bign &n){
  if(n.empty()) os<<0;
  for(int i=n.size()-1;i>=0;i--)os<<n[i];
  return os;
}
bool operator<(const bign &a,const bign &b){
  if(a.size()!=b.size()) return a.size()<b.size();
  for(int i=a.size()-1;i>=0;i--)
    if(a[i]!=b[i]) return a[i]<b[i];
  return 0;
}
bool operator>(const bign &a,const bign &b){return b<a;}
bool operator<=(const bign &a,const bign &b){return !(a>b);}
bool operator>=(const bign &a,const bign &b){return !(a<b);}
bool operator==(const bign &a,const bign &b){return (a<=b)&&(b<=a);}
bool operator!=(const bign &a,const bign &b){return !(a==b);}
bign& operator+=(bign &a,const bign &b){
  if(a.size()<b.size())a.resize(b.size());
  for(unsigned int i=0;i!=b.size();i++)a[i]+=b[i];
  return a.check();
}
bign operator+(bign a,const bign &b){return a+=b;}
bign& operator-=(bign &a,bign b){
  if(a<b) swap(a,b);
  for(unsigned int i=0;i!=b.size();a[i]-=b[i],i++){
    if(a[i]>=b[i])continue;
    int j=i+1;
    while(!a[j]) j++;
    while(j>i) --a[j],a[--j]+=10;
  }
  return a.check();
}
bign operator-(bign a,bign b){return a-=b;}//abs
bign operator*(const bign &a,const bign &b){
  bign n;
  n.assign(a.size()+b.size()-1,0);
  for(unsigned int i=0;i!=a.size();i++)
    for(unsigned int j=0;j!=b.size();j++)
      n[i+j]+=a[i]*b[j];
  return n.check();
}
bign& operator*=(bign &a,bign &b){return a=a*b;}
bign divmod(bign &a,const bign &b){
  bign ret,d,c;
  for(int t=a.size()-b.size();a>=b;--t){
    d.assign(t+1,0);d.back()=1;c=b*d;
    while(a>=c)a-=c,ret+=d;
  }
  return ret;
}
bign operator/(bign a,const bign &b){return divmod(a,b);}
bign operator/=(bign &a,const bign &b){return a=a/b;}
bign &operator%=(bign &a,const bign &b){divmod(a,b);return a;}
bign operator%(bign a,const bign &b){return a%=b;}
int main(){
  bign a,b;
  cin>>a>>b;
  cout<<a+b<<endl;
  if(a<b)cout<<"-";
  cout<<a-b<<endl;
  cout<<a*b<<endl;
  cout<<divmod(a,b)<<endl;
  cout<<a<<endl;
}