FirstBadVersion.java

/**
 * 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.
 *
 * isBadVersion function:
 * Given n = 5, and version = 4 is the first bad version.
 *
 * call isBadVersion(3) -> false
 * call isBadVersion(5) -> true
 * call isBadVersion(4) -> true
 *
 *
 * Time: O(logn), Space: O(1)
 */

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