题目
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.
解题思路
模拟两个数的加法，维护一个进位
代码
class Solution:
def addBinary(self, a: str, b: str) -> str:
def add(x, y, carry):
s = x + y + carry
return (s // 2, s % 2)
ml = max(len(a), len(b))
res = ''
carry = 0
a = a.rjust(ml, '0')
b = b.rjust(ml, '0')
for i in range(ml-1, -1, -1):
carry, s = add(int(a[i]), int(b[i]), int(carry))
res = str(s) + res
return '1' + res if carry else res
