LeetCode #278 First Bad Version
Problem
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.
Example:
Given n = 5, and version = 4 is the first bad version.call isBadVersion(3) -> false
call isBadVersion(5) -> true
call isBadVersion(4) -> trueThen 4 is the first bad version.
Solution
Use binary search to find the boundary between good and bas version. Be aware of the edge case of first bad version because it’s still a bad version. We have to drop the last comparison which is our target version.
Complexity
It’s obviously time complexity is O(logn) and space complexity is O(1).
