Add Binary

Problem

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

Solution Approach

Expected Time Complexity: $O(n)$

Click - to see solution code

C++

class Solution {
   public:
    string addBinary(string a, string b) {
        string s = "";

        int c = 0, i = a.size() - 1, j = b.size() - 1;
        while (i >= 0 || j >= 0 || c == 1) {
            c += i >= 0 ? a[i--] - '0' : 0;
            c += j >= 0 ? b[j--] - '0' : 0;
            s = char(c % 2 + '0') + s;
            c /= 2;
        }

        return s;
    }
};