first_bad_version_lc278.java

/* 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 left = 1;
        int right = n;
        int mid = 0;
        
        while (left < right) {
            mid = left + (right -left )/2;
            if (!isBadVersion(mid)){
                left = mid +1;
            } else {
                right = mid;
            }   
        }
        return left;       
    }
}