Add Binary (LeetCode) | Interview Question Explanation

AddBinary.cpp

class Solution {
public:
    string addBinary(string a, string b) {
        string res;
        int i = a.size() - 1, j = b.size() - 1;
        int sum, carry = 0;
        while(i >= 0 || j >= 0) {
            sum = carry;
            if(i >= 0) sum += a[i--] - '0';
            if(j >= 0) sum += b[j--] - '0';
            res += to_string(sum % 2);
            carry = sum / 2;
        }
        if(carry != 0) res += '1';
        reverse(res.begin(), res.end());
        return res;
    }
};