First bad version

problem [https://leetcode.com/problems/first-bad-version/ 278. First Bad Version].

Problem description


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  versions   and you want to find out the first bad one, which causes all the following ones to be bad.

You are given an API  which returns whether   is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.


 * Example 1
 * Input: n = 5, bad = 4
 * Output: 4
 * Explanation:
 * call  → false
 * call  → true
 * call  → true
 * Then 4 is the first bad version.


 * Example 2
 * Input: n = 1, bad = 1
 * Output: 1


 * Constraints