大数相加减

 代码：

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
const int maxn = 1000;
int a[maxn],b[maxn];
int main(){
    string s1,s2;
    cin>>s1>>s2;
    memset(a,0,sizeof(a));
    memset(b,0,sizeof(b));
    int len1= s1.length();
    int len2 = s2.length();
    for(int i=0;i<len1;i++){
        a[len1-i] = s1[i]-'0';
    }
    for(int i=0;i<len2;i++){
        b[len2-i] = s2[i]-'0';
    }
    int i=1;
    while(i<=len1||i<=len2){
        if(a[i]<b[i]){
            a[i+1]--;
            a[i]=a[i]+10;
        }
        a[i] = a[i]-b[i];
        i++;
    }
    int j;
    for(j=len1;j>=1;j--){
        if(a[j])
            break;
    }
    for(int k = j;k>=1;k--){
        cout<<a[k];
    }
    cout<<endl;
    return 0;
}

大数相加：

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
const int maxn = 1000;
int a[maxn],b[maxn];
int c[maxn];
int main(){
    string s1,s2;
    cin>>s1>>s2;
    memset(a,0,sizeof(a));
    memset(b,0,sizeof(b));
    memset(c,0,sizeof(c));
    int len1= s1.length();
    int len2 = s2.length();
    for(int i=0;i<len1;i++){
        a[len1-i] = s1[i]-'0';
    }
    for(int i=0;i<len2;i++){
        b[len2-i] = s2[i]-'0';
    }
    int i=1;
    int t = 0;
    while(i<=len1||i<=len2){
        t += a[i]+b[i];
        c[i] = t%10;
        t = t/10;
        i++;
    }
    if(t){
        c[i] = t;
    }
    else{
        i--;
    }
    
    for(int j = i;j>=1;j--){
        cout<<c[j];
    }
    cout<<endl;
    return 0;
}