题解 | #合并k个已排序的链表#

Java iterator

import java.util.*;

public class Solution {
    public ListNode mergeKLists(ArrayList<ListNode> lists) {
        if(lists==null||lists.size()==0) return null;

        Iterator it = lists.iterator();

        ListNode res = (ListNode)it.next();
        ListNode cur = null;
        while(it.hasNext()){
            cur = (ListNode)it.next();
            res = mergeList(res, cur);
        }
        return res;
    }

    private ListNode mergeList(ListNode l1, ListNode l2){

        ListNode head = new ListNode(0);
        ListNode tail = head;
        while(l1!=null&&l2!=null){
            if(l1.val>l2.val){
                tail.next = l2;
                l2 = l2.next;
            }else{
                tail.next = l1;
                l1 = l1.next;
            }
            tail = tail.next;
        }
        if(l1==null) tail.next = l2;
        else tail.next = l1;
        return head.next;
    }
}