c++ 大数加法 乘法 除法 （模板）

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstdlib>
#include <string>
#include <iostream>
#include <utility>
#include <cstdio>
const int N = 100009;
using namespace std;
 string ans[110];
char str[N];
struct Node
{
    int d[N];
    int len;

    Node() {memset(d, 0, sizeof(d));len=1;}
    Node(char *s)
    {
        memset(d, 0, sizeof(d));
        len = strlen(s);
        int i = 0;
        while(s[i] != '\0')
        {
            d[len-i-1] = s[i] - '0';
            ++i;
        }
    }

    int cmp(const Node &t)
    {
        int l = this->len - t.len;
        if(l < 0)
            return -1;

        int i;
        for(i=t.len-1;i>=0;i--)
        {
            if(this->d[i+l] < t.d[i])
                break;
            else if(this->d[i+l] > t.d[i])
            {
                return l;
            }
        }
        if(i < 0)
            return l;
        return l-1;
    }

    void change(int pos)
    {
        this->d[pos] += 1;
        int i = pos;
        while(this->d[i] > 9)
        {
            this->d[i] -= 10;
            this->d[i+1]++;
            ++i;
        }
        if(i+1 > this->len)
            this->len = i+1;
    }

    Node operator / (const Node &t)
    {
        Node ans;
        while(1)
        {
            int p = this->cmp(t);
            if(p == -1)
                break;
            else
            {
                ans.change(p);
                for(int i=0;i<t.len;i++)
                {
                    this->d[i+p+1]--;
                    this->d[i+p] = this->d[i+p]+10-t.d[i];
                    if(this->d[i+p] > 9)
                    {
                        this->d[i+p] -= 10;
                        this->d[i+1+p]++;
                    }
                }
                while(this->len > 1 && this->d[this->len - 1] == 0)
                    this->len--;
            }
        }

        return ans;
    }

};

string sum(string s1,string s2)  //大数加法
{
	if(s1.length()<s2.length())
	{
		string temp=s1;
		s1=s2;
		s2=temp;
	}
	int i,j;
	for(i=s1.length()-1,j=s2.length()-1;i>=0;i--,j--)
	{
		s1[i]=char(s1[i]+(j>=0?s2[j]-'0':0));   //注意细节
		if(s1[i]-'0'>=10)
		{
			s1[i]=char((s1[i]-'0')%10+'0');
			if(i) s1[i-1]++;
			else s1='1'+s1;
		}
	}
	return s1;
}

string Mult(string s,int x)  //大数乘以整形数
{
    reverse(s.begin(),s.end());
    int cmp=0;
    for(int i=0;i<s.size();i++)
    {
        cmp=(s[i]-'0')*x+cmp;
        s[i]=(cmp%10+'0');
        cmp/=10;
    }
    while(cmp)
    {
        s+=(cmp%10+'0');
        cmp/=10;
    }
    reverse(s.begin(),s.end());
    return s;
}
string Multfa(string x,string y)  //大数乘法
{
    string ans;
    for(int i=y.size()-1,j=0;i>=0;i--,j++)
    {
        string tmp=Mult(x,y[i]-'0');
        for(int k=0;k<j;k++)
            tmp+='0';
        ans=sum(ans,tmp);
    }
    return ans;
}

void chu(string xx,string yy)
{
    char x[9999],y[9999];
    for(int k=0;k<xx.size();k++)
            x[k]=xx[k];
    for(int k=0;k<yy.size();k++)
            y[k]=yy[k];

    strcpy(str,x);
    Node a(str);
    strcpy(str,y);
    Node b(str);
    Node ans = a / b;
    int e=0;char ss[9999];
    for(int i=ans.len-1;i>=0;i--)//商
        ss[e++]=ans.d[i]+'0';
    ss[e]=0;
    puts(ss);
    return ;
}

int main()
{
    string a,b;
    cin>>a>>b;
    cout<<Multfa(a,b)<<endl;//乘法 
    chu(a,b);//除法
    cout<<sum(a,b)<<endl;//加法
    return 0;
}