278. 第一个错误的版本

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