题解 | #牛群的合并#

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类一维数组 
     * @return ListNode类
     */
    public ListNode mergeKLists (ListNode[] lists) {

       if(lists.length==0){
        return null;
       }else if (lists.length==1){
        return lists[0];
       }


        ListNode headNode = lists[0];
        // write code here
        for(int i =1 ; i<lists.length;i++){
            headNode = mergeTwoLists(headNode,lists[i]);
        }

        return headNode;

    

    }
        public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if (l1 == null) {
            return l2;
        } else if (l2 == null) {
            return l1;
        } else if (l1.val < l2.val) {
            l1.next = mergeTwoLists(l1.next, l2);
            return l1;
        } else {
            l2.next = mergeTwoLists(l1, l2.next);
            return l2;
        }
    }
}