Design a Phone Directory which supports the following operations:

1. get : Provide a number which is not assigned to anyone.
2. check : Check if a number is available or not.
3. release : Recycle or release a number.

Example:

// Init a phone directory containing a total of 3 numbers: 0, 1, and 2.
PhoneDirectory directory = new PhoneDirectory(3);

// It can return any available phone number. Here we assume it returns 0.
directory.get();

// Assume it returns 1.
directory.get();

// The number 2 is available, so return true.
directory.check(2);

// It returns 2, the only number that is left.
directory.get();

// The number 2 is no longer available, so return false.
directory.check(2);

// Release number 2 back to the pool.
directory.release(2);

// Number 2 is available again, return true.
directory.check(2);

class PhoneDirectory {

    int[] arr;
    /** Initialize your data structure here
        @param maxNumbers - The maximum numbers that can be stored in the phone directory. */
    public PhoneDirectory(int maxNumbers) {
        arr = new int[maxNumbers];

        for (int i = 0; i < maxNumbers; i++){
            arr[i] = i;
        }
    }

    /** Provide a number which is not assigned to anyone.
        @return - Return an available number. Return -1 if none is available. */
    public int get() {
        for (int i = 0; i < arr.length; i++){
            if (arr[i] != -1){
                int ans = arr[i];
                arr[i] = -1;
                return ans;  
            } 
        }

        return -1;
    }

    /** Check if a number is available or not. */
    public boolean check(int number) {
        return arr[number] != -1;
    }

    /** Recycle or release a number. */
    public void release(int number) {
        arr[number] = number;
    }
}

/**
 * Your PhoneDirectory object will be instantiated and called as such:
 * PhoneDirectory obj = new PhoneDirectory(maxNumbers);
 * int param_1 = obj.get();
 * boolean param_2 = obj.check(number);
 * obj.release(number);
 */

class PhoneDirectory {

    Queue<Integer> available;
    Set<Integer> unused;

    /** Initialize your data structure here
        @param maxNumbers - The maximum numbers that can be stored in the phone directory. */
    public PhoneDirectory(int maxNumbers) {
        available = new LinkedList<>();
        unused = new HashSet<>();

        for (int i = 0; i < maxNumbers; i++){
            available.add(i);
            unused.add(i);
        }
    }

    /** Provide a number which is not assigned to anyone.
        @return - Return an available number. Return -1 if none is available. */
    public int get() {
        if (available.size() == 0){
            return -1;
        }

        unused.remove(available.peek());
        return available.poll();
    }

    /** Check if a number is available or not. */
    public boolean check(int number) {
        return unused.contains(number);
    }

    /** Recycle or release a number. */
    public void release(int number) {
        if (!unused.contains(number)){
            unused.add(number);
            available.add(number);
        }
    }
}

/**
 * Your PhoneDirectory object will be instantiated and called as such:
 * PhoneDirectory obj = new PhoneDirectory(maxNumbers);
 * int param_1 = obj.get();
 * boolean param_2 = obj.check(number);
 * obj.release(number);
 */