剑指OfferII 002.二进制加法

给定两个 01 字符串 a 和 b ，请计算它们的和，并以二进制字符串的形式输出。
输入为 非空 字符串且只包含数字 1 和 0。

示例 1:
输入: a = “11”, b = “10”
输出: “101”

来源：力扣（LeetCode）
链接：https://leetcode.cn/problems/JFETK5

class Solution(object):
    def addBinary(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        result = ''
        len1 = len(a)
        len2 = len(b)
        lens = max(len1, len2)
        num = abs(len1-len2)
        if len1 > len2:
            for i in range(num):
                b = '0' + b
        if len1 < len2:
            for i in range(num):
                a = '0' + a
        add_num = 0
        for j in range(lens-1, -1, -1):
            total_num = int(a[j]) + int(b[j]) + add_num
            add_num = total_num // 2
            true_num = total_num % 2
            result = str(true_num) + result
        if add_num > 0:
            result = str(add_num) + result
        return result

class Solution(object):
    def addBinary(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        result = bin(int(a, 2) + int(b, 2))
        return result[2:]