高精度运算类bign（非负整数）模板

#include
#include
using namespace std;

const int maxn = 200;
struct bign{   //定义类结构bign
  int len, s[maxn];

  bign() {     //bign()称为构造函数，目的在于对该储存大数的数组进行初始化
    memset(s, 0, sizeof(s));
    len = 1;
  }

  bign(int num) { //是为能够在main()函数中实现初始化而做的准备，如果没有这个将不能实现在定义bign x=1234形式
    *this = num;
  }

  bign(const char* num) {//同上也是为啦能够在main函数中实现初始化，bign x="1234";
    *this = num;
  }

  bign operator = (int num) {//此处是对输入num的转化为字符串
    char s[maxn];
    sprintf(s, "%d", num);//此函数作用与printf类似，不过是把num变量的数打印于s字符串中
    *this = s;
    return *this;
  }

  bign operator = (const char* num) {//将字符数组逆序，以方便运算时的进位问题
    len = strlen(num);
    for(int i = 0; i < len; i++) s[i] = num[len-i-1] - '0';
    return *this;
  }

  string str() const {//将字符数组组成一个字符串
    string res = "";
    for(int i = 0; i < len; i++) res = (char)(s[i] + '0') + res;
    if(res == "") res = "0";
    return res;
  }

  bign operator + (const bign& b) const{// 定义的加法运算
    bign c;
    c.len = 0;
    for(int i = 0, g = 0; g || i < max(len, b.len); i++) {
      int x = g;
      if(i < len) x += s[i];
      if(i < b.len) x += b.s[i];
      c.s[c.len++] = x % 10;
      g = x / 10;
    }
    return c;
  }

  void clean() {   //消除前导0
    while(len > 1 && !s[len-1]) len--;
  }

  bign operator * (const bign& b) {//定义乘法运算
    bign c; c.len = len + b.len;
    for(int i = 0; i < len; i++)
      for(int j = 0; j < b.len; j++)
        c.s[i+j] += s[i] * b.s[j];
    for(int i = 0; i < c.len-1; i++){
      c.s[i+1] += c.s[i] / 10;
      c.s[i] %= 10;
    }
    c.clean();
    return c;
  }

  bign operator - (const bign& b) {//减法运算
    bign c; c.len = 0;
    for(int i = 0, g = 0; i < len; i++) {
      int x = s[i] - g;
      if(i < b.len) x -= b.s[i];
      if(x >= 0) g = 0;
      else {
        g = 1;
        x += 10;
      }
      c.s[c.len++] = x;
    }
    c.clean();
    return c;
  }

  bool operator < (const bign& b) const{
    if(len != b.len) return len < b.len;
    for(int i = len-1; i >= 0; i--)
      if(s[i] != b.s[i]) return s[i] < b.s[i];
    return false;
  }

  bool operator > (const bign& b) const{
    return b < *this;
  }

  bool operator <= (const bign& b) {
    return !(b > *this);
  }

  bool operator == (const bign& b) {
    return !(b < *this) && !(*this < b);
  }

  bign operator += (const bign& b) {
    *this = *this + b;
    return *this;
  }
};

istream& operator >> (istream &in, bign& x) {//重新定义cin，让可以直接使用cin>>a
  string s;
  in >> s;
  x = s.c_str();
  return in;
}

ostream& operator << (ostream &out, const bign& x) {//重新定义cout,可以直接cout<   out << x.str();
  return out;
}

int main() {
  bign a,b;
  cin >> a>>b;
 
  cout << (a   return 0;
}