AddBinary-LCQ.cpp

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