Leetcode143. 重排链表

题目传送: ​​https://leetcode.cn/problems/reorder-list/​​

运行效率

代码如下：

class Solution {
    public void reorderList(ListNode head) {
    //双端队列
    ArrayDeque<ListNode> deque = new ArrayDeque<>();
    ListNode cur=head;
    while(cur != null){
      deque.add(cur);
      cur = cur.next;
    }
    int index=1;
    head=deque.poll();
    cur=head;
    while(!deque.isEmpty()){
      if(index%2==0){
          //取出队列的头部元素
        ListNode poll = deque.poll(); 
        cur.next=poll;
      }else{
            //取出队列的尾部元素
        ListNode listNode = deque.pollLast();
        cur.next=listNode;
      }
      index++;
      cur=cur.next;
    }
    cur.next=null;
  }
}