高精度整形数封装类。

　　操作符<<和>>注意使用友元标记，否则编译错误。

#include 
     
      #include 
      
       #include 
       
        using namespace std;struct bign {    vector
        
          num;            bign() {        num.push_back(0);    }    bign(const char* str) {        *this = str;    }    bign &operator = (const char* str) {        string s = str;        num.clear();        for (int i=s.size()-1; i>=0; --i) {            char c = s[i];            num.push_back(c - '0');        }        return *this;    }    bign operator + (const bign &n) const {        bign tmp;        tmp.num.clear();        int a = num.size();        int b = n.num.size();        int d = a > b ? b : a;        int c = 0;        for (int i=0; i
         
           b) {            for (int i=d; i
          
           =0; --i) { if (num[i] != n.num[i]) { return num[i] < n.num[i]; } } return false; } friend istream &operator >> (istream &in, bign &n) { string s; in >> s; n = s.c_str(); return in; } friend ostream &operator << (ostream &out, const bign &n) { for (int i=n.num.size()-1; i>=0; --i) { out << n.num[i]; } return out; }};int main() { bign n = "123"; bign m; m = "1123"; cout << n+m << endl; cout << (n
           
            << endl; return 0;}