刚好100行

#include<iostream>
using namespace std;

string tsub(string a,string b,bool t_a){
    int as,bs;
    if(t_a){
        as=a.size()-1;
        bs=b.size();
    }else{
        as=a.size();
        bs=b.size()-1;
    }
    int w=min(as,bs);
    int w2=max(as,bs);
    int z,t=0;
    string sum="";
    for (int i = 0;i<w;i++){
        z=a[i]-b[i]-t;
        if (z<0)t=1;
        else    t=0;
        sum=char(z+'0')+sum;
    }
    if (sum=="0"){
        return sum;
    }
    sum='-'+sum;
    return sum;
}

string add(string a,string b){
    int as=a.size(),bs=b.size();
    int k=0;
    if ((a[0]=='-') && (b[0]=='-')){
        k=1;
        for (int i=0;i<as-1;i++){
            a[i]=a[i+1];
        }
        as-=1;
        for (int i=0;i<bs-1;i++){
            b[i]=b[i+1];
        }
        bs-=1;
    }if ((a[0]=='-') && (b[0]!='-')){
        for (int i=0;i<as-1;i++){
            a[i]=a[i+1];
        }
        return tsub(a,b,true);
    }if ((a[0]!='-') && (b[0]=='-')){
        for (int i=0;i<bs-1;i++){
            b[i]=b[i+1];
        }
        // return "";
        return tsub(a,b,false);
    }
    string s="";
    for (int i = as-1;i>-1;i--){
        s=s+a[i];
    }
    a=s;
    s="";
    for (int i = bs-1;i>-1;i--){
        s=s+b[i];
    }
    b=s;
    long long w=min(as,bs);
    long long w2=max(as,bs);
    int j=0,z=0;
    string sum="";
    for (int i = 0;i<w;i++){
        z=a[i]-'0'+b[i]-'0'+j;
        if (z>=10){
            j=1;
        }else{
            j=0;
        }
        // cout << z<< ' ？';
        sum=char('0'+z-j*10)+sum;
    }
    for (int i = w;i<w2;i++){
        if (as>bs){z=a[i]-'0'+j;}
        else{ z=b[i]-'0'+j;}
        if (z>=10){
            j=1;
        }else{
            j=0;
        }
        sum=char('0'+z-j*10)+sum;
    }
    if (j){
        sum=char('0'+j)+sum;
    }
    if (!k)return sum;
    return '-'+sum;
}

int main(){
    string a,b;
    cin >> a >> b;
    cout << add(a,b);
}