题解 | #合并k个已排序的链表#两两比较

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
        ListNode head = null;
        ListNode ze = new ListNode(0);
        for (ListNode list : lists) {
            if(head ==null){
                head = list;
                continue;
            }
            if (list == null) {
                continue;
            }
            ListNode cur = ze;
            while (head != null && list != null) {
                if(head.val <= list.val){
                    cur.next = head;
                    head = head.next;
                }else{
                    cur.next = list;
                    list = list.next;
                }
                cur = cur.next;
            }
            if(head == null){
                cur.next = list;
                head = ze.next;
               ze = new ListNode(0);
            }else{
                cur.next = head;
                head = ze.next;
                ze = new ListNode(0);
            }

        }
        return head;
    }
}