67. Add Binary

Question 67

https://leetcode.com/problems/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"

Answer

v1. use bin() (100%)

v2. use Recursively (45%)

v1

class Solution:
    def addBinary(self, a, b):
        return ( bin(int(a,2)+int(b,2) ) )[2:]
            
    ## second way
    # return bin(eval('0b'+a) + eval('0b'+b))[2:]

v2

class Solution:
    def addBinary(self, a, b):

        if len(a) == 0:
            return b
        if len(b) == 0:
            return a
        
        if ( a[-1] == "1" and b[-1] == "1" ):
            return self.addBinary( self.addBinary( a[:-1], b[:-1] ), "1" ) + "0"
        elif( a[-1] == "0" and b[-1] == "0" ):
            return self.addBinary( a[:-1], b[:-1] ) + "0"
        else:
            return self.addBinary( a[:-1], b[:-1] ) + "1"