필기 데이터 구조 - 링크 기반 대기 열

package com.tc.javabase.datastructure.linklist.queue;

import com.tc.javabase.datastructure.queue.Queue;

/**
 * @Classname LinkedListQueue
 * @Description          
 *
 *                        
 *
 *        ：
 *  *    ：O(1)
 *  *    ：O(1)
 *  *        :O(1)
 *
 *
 * @Date 2020/7/18 18:42
 * @Created by zhangtianci
 */
public class LinkedListQueue implements Queue {
    private class Node{
        public E e;
        public Node next;
        public Node(E e, Node next) {
            this.e = e;
            this.next = next;
        }

        public Node(E e){
            this(e,null);
        }

        public Node(){
            this(null,null);
        }
    }

    private Node head,tail;
    private int size;

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0 ? true : false;
    }

    /**
     *   
     *
     *      ：O(1)
     * @param e
     */
    @Override
    public void enqueue(E e) {
        if (tail == null){
            tail = new Node(e);
            head = tail;
        }else {
            tail.next = new Node(e);
            tail = tail.next;
        }

        size++;
    }

    /**
     *    
     *       :O(1)
     * @return
     */
    @Override
    public E dequeue() {
        if (isEmpty()){
            throw new IllegalArgumentException("    ！");
        }
        Node retn = head;
        head = head.next;
        retn.next = null;
        if (head == null){
            tail = null;
        }
        size--;
        return retn.e;
    }

    /**
     *         
     *        :O(1)
     * @return
     */
    @Override
    public E getFront() {
        if (isEmpty()){
            throw new IllegalArgumentException("    ！");
        }
        return head.e;
    }

    @Override
    public String toString() {

        StringBuilder builder = new StringBuilder();
        builder.append("Queue head");
        Node curr = head;
        while (curr != null){
            builder.append(curr.e);
            builder.append("->");
            curr = curr.next;
        }
        builder.append("NULL tail");
        return builder.toString();
    }

    public static void main(String[] args) {

        LinkedListQueue queue = new LinkedListQueue<>();
        for(int i = 0 ; i < 10 ; i ++){
            queue.enqueue(i);
            System.out.println(queue);

            if(i % 3 == 2){
                queue.dequeue();
                System.out.println(queue);
            }
        }
    }
}