Jan 10, 2022 - 5 min ' read

Add Binary

Problem Statement - link #

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

Examples #

Example 1:

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

Example 2:

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

Constraints #

1 <= a.length, b.length <= 10^4
a and b consist only of ‘0’ or ‘1’ characters.
Each string does not contain leading zeros except for the zero itself.

Solutions #

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