July - Day 19 - Add Binary

Solution.py

# https://leetcode.com/explore/challenge/card/july-leetcoding-challenge/546/week-3-july-15th-july-21st/3395/

class Solution(object):
  def addBinary(self, a: str, b: str) -> str:
    return self.add(a, b, len(a) - 1, len(b) - 1, 0)
  
  def add(self, a: str, b: str, i: int, j: int, c: int):
    if c == 0 and i < 0 and j < 0:
      return ''
    
    v1 = int(a[i]) if i >= 0 else 0
    v2 = int(b[j]) if j >= 0 else 0
    
    current = v1 ^ v2 ^ c
    c = (v1 & v2) | ((v1 ^ v2) & c)
    
    return self.add(a, b, i - 1, j - 1, c) + str(current)