leetcode-grind/problems/278/main.py

# The isBadVersion API is already defined for you.
# @param version, an integer
# @return a bool
# def isBadVersion(version):

# I am assuming that the latest definitely is bad based on the way the problem is worded
# so I will just implement a binary search pretty mcuh

def isBadVersion(n):
    return n >= 4

class Solution:
    def firstBadVersion(self, n):
        # This check cuts out a case quickly, and also makes the logic easier to write
        # because negatives and zeros no longer have to be dealt with
        if isBadVersion(0):
            return 0
        knownGood = 0
        knownBad = n
        while knownBad - knownGood > 1:
            # find the mid point
            # check whether it's good or bad, and update accordingly
            mid = (knownGood + knownBad) // 2
            if isBadVersion(mid):
                knownBad = mid
            else:
                knownGood = mid
        return knownBad

s = Solution()
print("Expected: 4")
print("Got:", s.firstBadVersion(5))