first-bad-version.py

# Time:  O(logn)
# Space: O(1)
#
# 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.
#

# 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 - left) / 2
            if isBadVersion(mid):
                right = mid - 1
            else:
                left = mid + 1
        return left