(Leet Code c++)Add Binary

67. Add Binary

 

Given two binary strings a and b, return their sum as a binary string.

 

Example 1:

Input: a = "11", b = "1" Output: "100"

Example 2:

Input: a = "1010", b = "1011" Output: "10101"

 

Constraints:

• 1 <= a.length, b.length <= 104
• a and b consist only of '0' or '1' characters.
• Each string does not contain leading zeros except for the zero itself.

class Solution {
public:
    
    string addBinary(string a, string b) {
        string answer = "";
        int aIndex = a.size() - 1;
        int bIndex = b.size() - 1;
        int carry = 0;
        
        while((aIndex != -1 || bIndex != -1) || carry){
            if(aIndex >= 0){
                carry += a[aIndex--] == '1' ? 1 : 0;
            }
            if(bIndex >= 0){
                carry += b[bIndex--] == '1' ? 1 : 0;
            }
            
            answer = to_string(carry % 2) + answer;
            carry /= 2;
        }
        
        return answer;
    }
};