N0278. First Bad Version（Python）

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.

        你是产品经理，目前正领导一个团队开发新产品。 不幸的是，您的产品的最新版本未通过质量检查。 由于每个版本都是基于以前的版本开发的，因此版本较差的所有版本也都是不好的。
        假设你有n个版本[1,2，...，n]，并且你想找出第一个错误的版本，这会导致下面所有的错误。

        给你一个API布尔isBadVersion（版本），它将返回版本是否坏。 实现一个函数来查找第一个错误版本。 您应该尽量减少对API的调用次数。

思路：

    用二分查找的思想来解决此类问题。

代码：

# 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
        """
        left,right = 1,n
        while(left<right):
            mid = (left+right)/2
            if isBadVersion(mid):
                right = mid
            else:
                left = mid+1
        return left