[LeetCode] 379 Design Phone Directory

 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);

 

Constraints:

• 1 <= maxNumbers <= 10^4
• 0 <= number < maxNumbers
• The total number of call of the methods is between [0 - 20000]

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class PhoneDirectory { int Cap; Set<Integer> set0; Set<Integer> set1; /** Initialize your data structure here @param maxNumbers - The maximum numbers that can be stored in the phone directory. */ public PhoneDirectory(int maxNumbers) { Cap = maxNumbers; set0 = new HashSet<>(); set1 = new HashSet<>(); for(int i=0; i<Cap; ++i) set0.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() { Iterator<Integer> it = set0.iterator(); if(!it.hasNext()){ return -1; }else{ Integer v = it.next(); set0.remove(v); set1.add(v); return v; } } /** Check if a number is available or not. */ public boolean check(int number) { return set0.contains(number); } /** Recycle or release a number. */ public void release(int number) { set1.remove(number); set0.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); */