高精度模板

转自http://blog.csdn.net/wall_f/article/details/8373395

很不错的高精度模板，但这个模板只能算加、减、乘、除等基本运算，但操作减法的时候只能大数减小数，所以最重要的操作是 + 、 +=、*、*=、、/、/=、-=、==，>=，这些基本的运算，最近通过在UVA在刷的几道题，发现自己以前的模板存在一些BUG，现在贴上已经改正的模板，欢迎大家指出我的BUG。

#include <iostream>  
#include <cstdio>  
#include <cstdlib>  
#include <cstring>  
#include <string>  
#include <algorithm>  
using namespace std;  
  
const int MAXN = 410;  
  
struct bign  
{  
    int len, s[MAXN];  
    bign ()  
    {  
        memset(s, 0, sizeof(s));  
        len = 1;  
    }  
    bign (int num) { *this = num; }  
    bign (const char *num) { *this = num; }  
    bign operator = (const int num)  
    {  
        char s[MAXN];  
        sprintf(s, "%d", num);  
        *this = s;  
        return *this;  
    }  
    bign operator = (const char *num)  
    {  
        for(int i = 0; num[i] == '0'; num++) ;  //去前导0  
        len = strlen(num);  
        for(int i = 0; i < len; i++) s[i] = num[len-i-1] - '0';  
        return *this;  
    }  
    bign operator + (const bign &b) const //+  
    {  
        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;  
    }  
    bign operator += (const bign &b)  
    {  
        *this = *this + b;  
        return *this;  
    }  
    void clean()  
    {  
        while(len > 1 && !s[len-1]) len--;  
    }  
    bign operator * (const bign &b) //*  
    {  
        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; i++)  
        {  
            c.s[i+1] += c.s[i]/10;  
            c.s[i] %= 10;  
        }  
        c.clean();  
        return c;  
    }  
    bign operator *= (const bign &b)  
    {  
        *this = *this * b;  
        return *this;  
    }  
    bign operator - (const bign &b)  
    {  
        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;  
    }  
    bign operator -= (const bign &b)  
    {  
        *this = *this - b;  
        return *this;  
    }  
    bign operator / (const bign &b)  
    {  
        bign c, f = 0;  
        for(int i = len-1; i >= 0; i--)  
        {  
            f = f*10;  
            f.s[0] = s[i];  
            while(f >= b)  
            {  
                f -= b;  
                c.s[i]++;  
            }  
        }  
        c.len = len;  
        c.clean();  
        return c;  
    }  
    bign operator /= (const bign &b)  
    {  
        *this  = *this / b;  
        return *this;  
    }  
    bign operator % (const bign &b)  
    {  
        bign r = *this / b;  
        r = *this - r*b;  
        return r;  
    }  
    bign operator %= (const bign &b)  
    {  
        *this = *this % b;  
        return *this;  
    }  
    bool operator < (const bign &b)  
    {  
        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)  
    {  
        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)  
    {  
        return !(*this > b) && !(*this < b);  
    }  
    bool operator != (const bign &b)  
    {  
        return !(*this == b);  
    }  
    bool operator <= (const bign &b)  
    {  
        return *this < b || *this == b;  
    }  
    bool operator >= (const bign &b)  
    {  
        return *this > b || *this == b;  
    }  
    string str() const  
    {  
        string res = "";  
        for(int i = 0; i < len; i++) res = char(s[i]+'0') + res;  
        return res;  
    }  
};  
  
istream& operator >> (istream &in, bign &x)  
{  
    string s;  
    in >> s;  
    x = s.c_str();  
    return in;  
}  
  
ostream& operator << (ostream &out, const bign &x)  
{  
    out << x.str();  
    return out;  
}  
  
int main()  
{  
    bign a, b, c, d, e, f, g;  
    while(cin>>a>>b)  
    {  
        a.clean(), b.clean();  
        c = a+b;  
        d = a-b;  
        e = a*b;  
        f = a/b;  
        g = a%b;  
        cout<<"a+b"<<"="<<c<<endl; // a += b  
        cout<<"a-b"<<"="<<d<<endl; // a -= b;  
        cout<<"a*b"<<"="<<e<<endl; // a *= b;  
        cout<<"a/b"<<"="<<f<<endl; // a /= b;  
        cout<<"a%b"<<"="<<g<<endl; // a %= b;  
        if(a != b) printf("YES\n");  
        else printf("NO\n");  
    }  
    return 0;  
}