题解 | #链表排序#

1、利用优先队列

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode sortList (ListNode head) {
        // write code here
        if (head == null || head.next == null) return head;
        Queue<ListNode> queue = new PriorityQueue<>((a, b) -> a.val - b.val);
        ListNode cur = head;
        while (cur != null) {
            queue.offer(cur);
            cur = cur.next;
        }
        ListNode dummy = new ListNode(0);
        cur = dummy;
        while (!queue.isEmpty()) {
            cur.next = queue.poll();
            cur = cur.next;
        }
        cur.next = null;
        return dummy.next;
    }
}