Leetcode 278 First Bad Version

最新推荐文章于 2020-11-10 09:28:36 发布

转载最新推荐文章于 2020-11-10 09:28:36 发布 · 71 阅读

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原文链接：http://www.cnblogs.com/lilixu/p/5490259.html

本文介绍了一种使用二分查找的方法来高效确定首次出现故障的产品版本。假设产品版本按线性序列排列，且一旦某个版本开始出现故障，之后的所有版本都将受到影响。通过调用一个名为isBadVersion的API来判断特定版本是否出现了故障，并以此为基础实现了firstBadVersion函数。

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.

基本二分查找

class Solution(object):
    def firstBadVersion(self, n):
        a, b,ans = 1, n, 1
        while a <= b:
            x = a + (b-a)/2
            if isBadVersion(x):
                ans = x
                b = x-1
            else:
                a = x+1
        return ans