content: /**
   * File: deque.dart
   * Created Time: 2023-03-28
   * Author: liuyuxin (gvenusleo@gmail.com)
   */
  
  import 'dart:collection';
  
  void main() {
    /* 初始化双向队列 */
    final Queue<int> deque = Queue();
    deque.addFirst(3);
    deque.addLast(2);
    deque.addLast(5);
    print("双向队列 deque = $deque");
  
    /* 访问元素 */
    final int peekFirst = deque.first;
    print("队首元素 peekFirst = $peekFirst");
    final int peekLast = deque.last;
    print("队尾元素 peekLast = $peekLast");
  
    /* 元素入队 */
    deque.addLast(4);
    print("元素 4 队尾入队后 deque = $deque");
    deque.addFirst(1);
    print("元素 1 队首入队后 deque = $deque");
  
    /* 元素出队 */
    final int popLast = deque.removeLast();
    print("队尾出队元素 = $popLast ，队尾出队后 deque = $deque");
    final int popFirst = deque.removeFirst();
    print("队首出队元素 = $popFirst ，队首出队后 deque = $deque");
  
    /* 获取双向队列的长度 */
    final int size = deque.length;
    print("双向队列长度 size = $size");
  
    /* 判断双向队列是否为空 */
    final bool isEmpty = deque.isEmpty;
    print("双向队列是否为空 = $isEmpty");
  }
  