# LeetCode – Design Phone Directory (Java)

Design a Phone Directory which supports the following operations:

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

Java Solution 1

```public class PhoneDirectory { int max; HashSet<Integer> set; LinkedList<Integer> queue;   /** Initialize your data structure here @param maxNumbers - The maximum numbers that can be stored in the phone directory. */ public PhoneDirectory(int maxNumbers) { set = new HashSet<Integer>(); queue = new LinkedList<Integer>(); for(int i=0; i<maxNumbers; i++){ queue.offer(i); } max=maxNumbers-1; }   /** Provide a number which is not assigned to anyone. @return - Return an available number. Return -1 if none is available. */ public int get() { if(queue.isEmpty()) return -1;   int e = queue.poll(); set.add(e); return e; }   /** Check if a number is available or not. */ public boolean check(int number) { return !set.contains(number) && number<=max; }   /** Recycle or release a number. */ public void release(int number) { if(set.contains(number)){ set.remove(number); queue.offer(number); } } }```
Category >> Algorithms
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