278 First Bad Version
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
[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
versionis bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.
The Idea: Binary search until we are able to converge into the region that separates the last good version to the first bad version.
[1 1 1 1 1 1 1 1 1 1 0 0 0 0 0]
Complexity: O(logn) time and O(1) space through iterative binary search
# The isBadVersion API is already defined for you.
# @param version, an integer
# @return a bool
# def isBadVersion(version):
def firstBadVersion(self, n):
:type n: int
left, right = 1, n
while left < right:
mid = int(left + ((right - left) >> 1))
if not isBadVersion(mid): # search right
left = mid + 1
else: # search left
right = mid - 1
return left + 1