题解 | #合并k个已排序的链表#

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 lists ListNode类ArrayList
     * @return ListNode类
     */
    public ListNode mergeKLists (ArrayList<ListNode> lists) {
        // write code here
        List<Integer> a = new ArrayList();
        for (ListNode node : lists) {
            while (node != null) {
                a.add(node.val);
                node = node.next;
            }
        }
        Collections.sort(a);
        ListNode head = null;
        ListNode pre = null;
        for (int i : a) {
            ListNode newNode = new ListNode(i);
            if (head == null) {
                head = newNode;
                pre = head;
            } else {
                pre.next = newNode;
                pre = newNode;
            }
        }
        return  head;
    }
}

返回的链表和原链表其实没有什么关系。