LeetCode: First Bad Version

## https://code.dennyzhang.com/first-bad-version
## Basic Ideas: Binary search
##         Find the first False
##         F F F F T T
##         T T
##      Hint: how to update index, if mid is F?
# 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 = int(left + (right-left)/2)
            if isBadVersion(mid):
                right = mid
            else:
                left = mid + 1
        # left == right
        return left if isBadVersion(left) else None