278. First Bad Version

# Easy

Find the first position of target using binary search

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

public class Solution extends VersionControl {
    public int firstBadVersion(int n) {
        int firstBad = n;
        int start = 1, end = n;
        while(start <= end) {
            int mid = start + (end - start)/2;
            if(isBadVersion(mid)) {
                firstBad = mid;
                end = mid - 1;
            } else
                start = mid + 1;
        }
        return firstBad;
    }
}a