【leetcode刷题】T186-二进制求和

示例 1:
输入: a = "11", b = "1"
输出: "100"

示例 2:
输入: a = "1010", b = "1011"
输出: "10101"

class Solution(object):
    def addBinary(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        if len(a) < len(b):
            a, b = b, a
        res = ''
        tmp = 0
        for i in range(1, len(b) + 1):
            tmp += int(a[-i]) + int(b[-i])
            res += str(tmp % 2)
            if tmp >= 2:
                tmp = 1
            else:
                tmp = 0


        if tmp == 0:
            res = a[:-len(b)] + res[::-1]
            return res

        # 其余a元素
        for i in range(len(b)+1, len(a)+1):
            tmp += int(a[-i])
            res += str(tmp % 2)
            if tmp >= 2:
                tmp = 1
            else:
                tmp = 0

        if tmp == 1:
            res += '1'
        return res[::-1]