addBinary

#include<iostream>
#include<bits/stdc++.h>
using namespace std;
string addBinary(string a,string b){
int carry=0;
    string res="";
    reverse(a.begin(),a.end()); 
    reverse(b.begin(),b.end());
    int i=0,sum;
    while(i<a.size() || i<b.size())
    {
        sum= carry;
        if(i<a.size()) sum+= a[i]-'0';
        if(i<b.size()) sum+= b[i]-'0';
        if(sum==0) carry=0, res+='0';
        else if(sum==1)  carry=0, res+='1';
        else if(sum==2)carry=1, res+='0';
        else carry=1, res+='1';
        i++;
    }
    if(carry==1)  res+='1';
    reverse(res.begin(),res.end());
    return res;
        
}
int main()
{
  string a = "1010"; 
  string b = "1011";
  cout<<addBinary(a,b)<<endl;
}