67. Add Binary

Given two binary strings, return their sum (also a binary string).

The input strings are both non-empty and contains only characters 1 or 0.

Example 1:

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

Example 2:

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

Constraints:

• Each string consists only of '0' or '1' characters.

• 1 <= a.length, b.length <= 10^4

• Each string is either "0" or doesn't contain any leading zero.

# @param {String} a
# @param {String} b
# @return {String}
def add_binary(a, b)
  (a.to_i(2) + b.to_i(2)).to_s(2)
end