278. First Bad Version.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 l = 0, r = n;
        while(l <= r){
            int m = l + (r - l) / 2;
            if(isBadVersion(m)) r = m - 1;
            else l = m + 1;
        }
        return l;
    }
}