Leetcode 67. Add Binary

You are given two binary strings a and b, return their sum as a binary string.

Examples

Example 1

Input:  a = "101", b = "10"
Output: "111"

Example 2

Input:  a = "10010", b = "111"
Output: "11001"

Constraints

• 1 <= a.length, b.length <= 10,000
• a and b consist only of '0' or '1' characters.
• Each string does not contain leading zeros except for the zero itself.