因为自己使用STL库比较多，对于字符串的处理多是用的string处理，对于高精度问题，用string的不太多，于是自己写了个string的高精度。代码：

#include<iostream>
#include<string> 
#include<algorithm>
using namespace std;
string pluss(string s1,string s2){//函数名为plus可能与系统函数重复
    reverse(s1.begin(),s1.end());
    reverse(s2.begin(),s2.end());
    int m=s1.length();
    int n=s2.length();
    int flag=0;
    string res;
    if(m>=n){
        for(int i=0;i<m;i++){
            if(i<n){
                int sum = s1[i]-'0'+s2[i]-'0'+flag;
                char c = sum%10+'0';
                res += c;
                flag = sum/10;
            }
            else {
                int sum = s1[i]-'0'+flag;
                char c = sum%10+'0';
                res += c;
                flag = sum/10;
            }
        }
    }
    else{
        for(int i=0;i<n;i++){
            if(i<m){
                int sum = s1[i]-'0'+s2[i]-'0'+flag;
                char c = sum%10+'0';
                res += c;
                flag = sum/10;
            }
            else {
                int sum = s2[i]-'0'+flag;
                char c = sum%10+'0';
                res += c;
                flag = sum/10;
            }
        }
    }
    reverse(res.begin(),res.end());
    return res;
}
int main(){
    string s = pluss("55454654687687654687678687687687687686786876786546786467864678687654687654678654675","1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111");
    cout<<s<<endl;
    return 0;
}