[leetcode: Python]278.First Bad Version

题目：
You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.

Suppose you have n versions [1, 2, …, n] and you want to find out the first bad one, which causes all the following ones to be bad.

You are given an API bool isBadVersion(version) which will return whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.

二分查找

方法一：性能46ms

# The isBadVersion API is already defined for you.# @param version, an integer# @return a bool# def isBadVersion(version):class Solution(object):    def firstBadVersion(self, n):        """        :type n: int        :rtype: int        """        low, high = 1, n        while low <= high:            mid = (low + high) / 2             res = isBadVersion(mid)            if res:                high = mid - 1            else:                low = mid + 1        return low

方法二：性能39ms

# The isBadVersion API is already defined for you.# @param version, an integer# @return a bool# def isBadVersion(version):class Solution(object):    def firstBadVersion(self, n):        """        :type n: int        :rtype: int        """        start = 1        end = n        while start + 1 < end:            mid = start + (end - start) / 2            if isBadVersion(mid):                end = mid            else:                start = mid        if isBadVersion(start):            return start        return end