题解 | 单链表的排序

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head ListNode类 the head node
     * @return ListNode类
     */
    public ListNode sortInList (ListNode head) {
        if (head == null || head.next == null) {
            return head;
        }
        PriorityQueue<ListNode> listNodes = new PriorityQueue<>(Comparator.comparing(
                    node -> node.val));
        ListNode currentNode = head;
        while (currentNode != null) {
            listNodes.add(currentNode);
            currentNode =  currentNode.next;
        }

        ListNode result = null;
        //上一个节点
        ListNode preNode = null;

        while (true) {
            ListNode peek = listNodes.poll();
            if (peek == null) {
                break;
            }
            if (result == null) {
                result = peek;
            } else {
                preNode.next = peek;
            }
            preNode = peek;
        }
        assert preNode != null;
        preNode.next = null;
        return result;

    }
}