First Bad Version

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.

Solution:

Can be like this way: n = 100 是个自然数，而不是数组，这里的函数可以传递给第几个版本，然后告诉你这个版本是否是坏的。

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class Solution:
    """
    @param n: An integers.
    @return: An integer which is the first bad version.
    """
    def findFirstBadVersion(self, n):
        start, end = 1, n
        while start + 1 < end:
            mid = (start + end) / 2
            if SVNRepo.isBadVersion(mid):
                end = mid
            else:
                start = mid
        if SVNRepo.isBadVersion(start):
            return start
        return end