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  • [LC] 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);

    class PhoneDirectory {
    
        /** Initialize your data structure here
            @param maxNumbers - The maximum numbers that can be stored in the phone directory. */
        private Queue<Integer> queue;
        private Set<Integer> used;
        public PhoneDirectory(int maxNumbers) {
            queue = new LinkedList<>();
            used = new HashSet<>();
            for (int i = 0; i < maxNumbers; i++) {
                queue.offer(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 (queue.isEmpty()) {
                return -1;
            }
            int num = queue.poll();
            used.add(num);
            return num;
        }
        
        /** Check if a number is available or not. */
        public boolean check(int number) {
            return !used.contains(number);
        }
        
        /** Recycle or release a number. */
        public void release(int number) {
            if (used.remove(number)) {
                queue.offer(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);
     */
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  • 原文地址:https://www.cnblogs.com/xuanlu/p/12020748.html
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