67.二进制求和
class Solution: def addBinary(self, a: str, b: str) -> str: result, carry, val = '', 0, 0 for i in range(max(len(a), len(b))): val = carry if i < len(a): val += int(a[-(i+1)]) if i < len(b): val += int(b[-(i+1)]) carry, val = val//2, val%2 result += str(val) if carry: result += str(1) return result[::-1]