N0278. First Bad Version（Python）

題目：

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.

        你是產品經理，目前正領導一個團隊開發新產品。 不幸的是，您的產品的最新版本未通過質量檢查。 由於每個版本都是基於以前的版本開發的，因此版本較差的所有版本也都是不好的。
        假設你有n個版本[1,2，...，n]，並且你想找出第一個錯誤的版本，這會導致下面所有的錯誤。

        給你一個API布爾isBadVersion（版本），它將返回版本是否壞。 實現一個函數來查找第一個錯誤版本。 您應該儘量減少對API的調用次數。

思路：

    用二分查找的思想來解決此類問題。

代碼：

# 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