LHL算法入门经典 5.2.3 高精度运算类bign

5.2.3 高精度运算类bign

#include<stdio.h>
#include<string.h>
#include<math.h>
const int maxn=1000;
struct bign
{int len,s[maxn];bign(){memset(s,0,sizeof(s));len=1;}//构造函数bign operator =(const char* num)//运算符重载{len=strlen(num);for(int i=0;i<len;i++)s[i]=num[len-i-1]-'0';return *this;}bign operator =(int num)//运算符重载{char s[maxn];sprintf(s,"%d",num);*this=s;return this;}bign(int num){*this=num;}//构造函数重载bign(const char* num){*this=num;}string str() const{string res="";for(int i=0;i<len;i++)res=(char)(s[i]+'0')+res;//字符串用加号连接if(res=="")res="0";return res;}bign operator + (const bign& b) const//重载运算符 +{bign c;//两数之和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];//大数每位相加if(i<b.len)x+=b.s[i];c.s[c.len++]=x%10;//每位不超过9g=x/10;//进位}return c;}bool operator < (const bign& b) const//重载运算符 <{if(len!=b.len)return len<b.len;//位数不同，长度比较结果与大小比较结果一致，true或falsefor(int i=len-1;i>=0;i--)if(s[i]!=b.s[i])return s[i]<b.s[i];//位数相同，结果与每位数字的比较结果一致return false;}};istream& operator >> (istream &in,bign& x)
{string s;in>>s;x=s.c_str();//c_str()是string类中的一个函数，返回当前字符串的首地址return in;
}ostream& operator >> (ostream &in,bign& x)
{out<<x.str();return out；
}
int main()
{return 0;
}