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
        ListNode rst = new ListNode(-1001);
        if(lists.size()==0){
            return null;
        }
        rst.next = lists.get(0);
        for(int i = 1; i < lists.size(); i++){
            rst = addNode(rst,lists.get(i));
        }
        return rst.next;
    }
    public ListNode addNode(ListNode rst,ListNode tgt){
        ListNode now = new ListNode(-1001);
        now.next = tgt;
        ListNode node;
        ListNode nur = new ListNode(-1001);
        nur = rst;
        while(now.next!=null){
            node = now.next;
            now.next = node.next;
            node.next = null;
            while(nur.next!=null && node.val > nur.next.val){
                nur = nur.next;
            }
            if(nur.next!=null){
                node.next = nur.next;
                nur.next = node;
            }else{
                nur.next =node;
                node.next = now.next;
                break;
            }
        }
        return rst;
    }
}