Add Binary Solutions in C++

// Source : https://oj.leetcode.com/problems/add-binary/
// Author : Hao Chen
// Date   : 2014-07-05



#include <iostream>
#include <string>
using namespace std;

string addBinary(string a, string b) {
    int alen = a.size();
    int blen = b.size();
    bool carry = false;
    string result;
    while( alen>0 || blen>0) {
        int abit = alen<=0 ? 0 : a[alen-1]-'0';
        int bbit = blen<=0 ? 0 : b[blen-1]-'0';
        int cbit = carry ? 1 : 0;
        result.insert(result.begin(), '0' + ((abit+bbit+cbit) & 1) );
        carry = (abit+bbit+cbit>1);
        alen--; blen--;
    }
    if (carry){
        result.insert(result.begin(), '1');
    }
    return result;
}


int main(int argc, char** argv) 
{
    string a = "11";
    string b = "1";
    if (argc>2){
        a = argv[1];
        b = argv[2];
    }

    cout << a << "+" << b << "=" << addBinary(a, b) << endl;
    
}

#include <string>
using std::string;

class Solution {
public:
    string addBinary(string a, string b) {
        string ret;
        bool carry{false};
        for (auto apos=a.size(), bpos=b.size(); apos || bpos || carry; ) {
            bool abit{apos && a[--apos] == '1'};
            bool bbit{bpos && b[--bpos] == '1'};
            ret = (abit ^ bbit ^ carry ? "1" : "0") + ret;
            carry = abit + bbit + carry >= 2;
        }
        return ret;
    }
};

/// Source : https://leetcode.com/problems/add-binary/description/
/// Author : liuyubobobo
/// Time   : 2018-06-03

#include <iostream>

using namespace std;

/// Simulation
/// Time Complexity: O(max(len(a), len(b)))
/// Space Complexity: O(1)
class Solution {
public:
    string addBinary(string a, string b) {

        string res = a.size() > b.size() ? a : b;
        string adder = a.size() > b.size() ? b : a;

        int index = res.size() - 1;
        for(int i = adder.size() - 1 ; i >= 0 ; i --){
            res[index] += adder[i] - '0';
            index --;
        }

        for(int i = res.size() - 1 ; i > 0 ; i --)
            if(res[i] > '1'){
                res[i - 1] += 1;
                res[i] = '0' + (res[i] - '0') % 2;
            }

        if(res[0] > '1'){
            res[0] = '0' + (res[0] - '0') % 2;
            res = '1' + res;
        }
        return res;
    }
};


int main() {

    cout << Solution().addBinary("11", "1") << endl;
    cout << Solution().addBinary("1010", "1011") << endl;

    return 0;
}