模板-高精度BigInteger

#include <bits/stdc++.h>

using namespace std;

struct BigInteger {

  static const int BASE = 100000000;

  static const int WIDTH = 8;

  vector<int> s;

  BigInteger(long long num = 0) { *this = num; } // 构造函数

  BigInteger operator = (long long num) { // 赋值运算符

    s.clear();

    do {

      s.push_back(num % BASE);

      num /= BASE;

    } while(num > 0);

    return *this;

  }

  BigInteger operator = (const string& str) { // 赋值运算符

    s.clear();

    int x, len = (str.length() - 1) / WIDTH + 1;

    for(int i = 0; i < len; i++) {

      int end = str.length() - i*WIDTH;

      int start = max(0, end - WIDTH);

      sscanf(str.substr(start, end-start).c_str(), "%d", &x);

      s.push_back(x);

    }

    return *this;

  }

  BigInteger operator + (const BigInteger& b) const {

    BigInteger c;

    c.s.clear();

    for(int i = 0, g = 0; ; i++) {

      if(g == 0 && i >= s.size() && i >= b.s.size()) break;

      int x = g;

      if(i < s.size()) x += s[i];

      if(i < b.s.size()) x += b.s[i];

      c.s.push_back(x % BASE);

      g = x / BASE;

    }

    return c;

  }

  BigInteger operator * (const BigInteger& b) const {

    BigInteger c;

    c.s.clear();

    for(int i = 0, g = 0; ; i++) {

      if(g == 0 && i >= s.size() && i >= b.s.size()) break;

      int x = 1;

      if(i < s.size()) x *= s[i];

      if(i < b.s.size()) x *= b.s[i];

      x+=g;

      c.s.push_back(x % BASE);

      g = x / BASE;

    }

    return c;

  }

};

ostream& operator << (ostream &out, const BigInteger& x) {

  out << x.s.back();

  for(int i = x.s.size()-2; i >= 0; i--) {

    char buf[20];

    sprintf(buf, "%08d", x.s[i]);

    for(int j = 0; j < strlen(buf); j++) out << buf[j];

  }

  return out;

}

istream& operator >> (istream &in, BigInteger& x) {

  string s;

  if(!(in >> s)) return in;

  x = s;

  return in;

}

int main() {

	return 0;

}