题解 | 单链表的排序-小顶堆

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) {
        // write code here
        ListNode dummy = new ListNode(1);
        PriorityQueue<ListNode> pq = new PriorityQueue<>((o1, o2)->o1.val - o2.val);
        while (head != null) {
            ListNode temp = head;
            head = head.next;
            temp.next = null;
            pq.add(temp);
        }
        ListNode ptr = dummy;
        while (!pq.isEmpty()) {
            ptr.next = pq.poll();
            ptr = ptr.next;
        }
        return dummy.next;
    }
}