高精

加

#include<bits/stdc++.h>
using namespace std;
char a[501],b[501];
int a1[501],b1[501];
int c[501],c1;
int main(){
	int r;
	scanf("%s",a);
	scanf("%s",b);
	int n=strlen(a);
	int m=strlen(b);
	for(int i=0;i<n;i++)a1[n-i]=a[i]-48;
	for(int i=0;i<m;i++)b1[m-i]=b[i]-48;
	int cl=1;
	r=0;
	while( (c1<=n) || (c1<=m))
	{
		c[c1]=a1[c1]+b1[c1]+r;
		r=c[c1]/10;
		c[c1]=c[c1]% 10;
		c1++;
	}
	c[c1]=r;
	if(c[c1]==0)c1--;
	for(int i=c1;i>=1;i--)cout<<c[i];
return 0;
}

减

#include<bits/stdc++.h>

using namespace std;

char a[10087],b[10087];
int na[10090], nb[10090], nc[10090]; 

int main()
{
    cin>>a>>b;
    if((strlen(a)<strlen(b)) || ( strcmp(a,b)<0 && strlen(a)==strlen(b)))
    {
        swap(a,b);
        cout<<"-";
    }
    
    int l1=strlen(a),l2=strlen(b),l3;
    
    for(int i=0;i<l1;i++) na[l1-i]=a[i]-'0';
    for(int i=0;i<l2;i++) nb[l2-i]=b[i]-'0';
  
    for(int i=1;i<=l1||i<=l2;i++)
    {
    	
        if(na[i]<nb[i])
        {
            na[i+1]--;
            na[i]+=10;
        }
        
        nc[i]=na[i]-nb[i];
        
        l3=i;
    }

    while(nc[l3]==0&&l3>1) l3--;


    for(int i=l3;i>0;i--)cout<<nc[i];

    return 0;
}

乘

#include <iostream>
#include <cstring>
using namespace std;
int a[300], b[300], c[300];
char s1[300], s2[300], s3[300];
 
int main()
{
    cin >> s1 >> s2;
    int la, lb, len;
    la = strlen(s1);
    lb = strlen(s2);
    for(int i=1;i<=la;i++)
        a[i] = s1[la-i] - 48;
    for(int i=1;i<=lb;i++)
        b[i] = s2[lb-i] - 48;
    for(int i=1;i<=la;i++)
        for(int j=1;j<=lb;j++)
        {
            c[i+j-1] = c[i+j-1] + a[i] * b[j];
            c[i+j] = c[i+j] + c[i+j-1]/10;
            c[i+j-1] = c[i+j-1] % 10;
        }
    len = la + lb;
    while(c[len]==0 && len>1)
        len--;     
    for(int i=len;i>=1;i--)
        cout << c[i];
     
    return 0;
}