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  • 高精度加法和乘法

    今天偶然看了一下某大神的模板,不经意翻到这个就顺便“借”了一下
    上代码吧:

    /*
    Date : 2015-8-21 晚上
    Author : ITAK
    
    Motto :
    
    今日的我要超越昨日的我,明日的我要胜过今日的我;
    以创作出更好的代码为目标。不断地超越自己。
    */
    #include <iostream>
    #include <cstdio>
    #include <cstring>
    using namespace std;
    /**
    怎样用:
    1、变量声明:能够给初值,如:BigInt ans=100;
                 能够不给初值(默觉得0)。如BigInt ans。
    2、计算:能够连个BigInt对象相乘,相加;ans+ans*ans;
             也能够和整数相乘相加。如:ans+78*ans;
    */
    
    
    struct BigInt  
    {  
        const static int mod = 10000;  
        const static int DLEN = 4;  
        int a[600],len;  
        BigInt()  
        {  
            memset(a,0,sizeof(a));  
            len = 1;  
        }  
        BigInt(int v)  
        {  
            memset(a,0,sizeof(a));  
            len = 0;  
            do  
            {  
                a[len++] = v%mod;  
                v /= mod;  
            }  
            while(v);  
        }  
        BigInt(const char *s)  
        {  
            memset(a,0,sizeof(a));  
            int L = strlen(s);  
            len = L/DLEN;  
            if(L%DLEN)
                len++;  
            int index = 0;  
            for(int i=L-1; i>=0; i-=DLEN)  
            {  
                int t = 0;  
                int k = i-DLEN+1;  
                if(k<0)
                    k = 0;  
                for(int j=k; j<=i; j++)  
                    t = t*10+s[j]-'0';  
                a[index++] = t;  
            }  
        }  
        BigInt operator +(const BigInt &b)const  
        {  
            BigInt res;  
            res.len = max(len,b.len);  
            for(int i=0; i<=res.len; i++)  
            {  
                res.a[i] = 0;  
            }  
            for(int i=0; i<res.len; i++)  
            {  
                res.a[i] += ((i<len)?

    a[i]:0)+((i<b.len)?b.a[i]:0); res.a[i+1] += res.a[i]/mod; res.a[i] %= mod; } if(res.a[res.len]>0) res.len++; return res; } BigInt operator *(const BigInt &b)const { BigInt res; for(int i=0; i<len; i++) { int up = 0; for(int j=0; j<b.len; j++) { int temp = a[i]*b.a[j]+res.a[i+j]+up; res.a[i+j] = temp%mod; up = temp/mod; } if(up != 0) res.a[i+b.len] = up; } res.len = len+b.len; while(res.a[res.len-1]==0 && res.len>1)res.len--; return res; } void output() { printf("%d",a[len-1]); for(int i=len-2; i>=0; i--) printf("%04d",a[i]); printf(" "); } };

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  • 原文地址:https://www.cnblogs.com/cxchanpin/p/7222032.html
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