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 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.

/* The isBadVersion API is defined in the parent class VersionControl.
      boolean isBadVersion(int version); */

public class FirstBadVersion extends VersionControl {
    public int firstBadVersion(int n) {
        int start = 1;
        int end = n;
       
        while(start < end) {
            int mid = start + (end - start) / 2;

            if(!isBadVersion(mid)) {
                start = mid + 1;
            } else {
                end = mid;
            }
        }
       
        return start;
    }
}