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 low = 1, high = n;
        while(low < high) {
            int mid = low + (high-low)/2;
            boolean answer = isBadVersion(mid);
            if(answer==false) {
                low = mid+1;
            }
            else {
                high = mid;
            }
        }
        return low;
    }
}