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 result = null;
        for (int i = 0; i < lists.size(); i++) {
            result = merge(result, lists.get(i));
        }
        return result;

    }

//合并两个
    private ListNode merge(ListNode n1, ListNode n2) {
        if (n1 == null || n2 == null) {
            return n1 != null ? n1 : n2;
        }
        if (n1.val <= n2.val) {
            n1.next = merge(n1.next, n2);
            return n1;
        } else {
            n2.next = merge(n2.next, n1);
            return n2;
        }
    }








}