LeetCode 23. 合并K个排序链表(Merge Two Sorted Lists)

Posted 2021-12-15 hglibin

23. 合并K个排序链表
23. Merge k Sorted Lists

题目描述
合并 k 个排序链表，返回合并后的排序链表。请分析和描述算法的复杂度。

LeetCode23. Merge k Sorted Lists困难

示例:

输入:
[
??1->4->5,
??1->3->4,
??2->6
]
输出: 1->1->2->3->4->4->5->6

Java 实现

public class ListNode 
    int val;
    ListNode next;

    ListNode(int x) 
        val = x;
    

import java.util.Comparator;
import java.util.PriorityQueue;

class Solution 
    public ListNode mergeKLists(ListNode[] lists) 
        if (lists == null || lists.length == 0) 
            return null;
        
        PriorityQueue<ListNode> queue = new PriorityQueue<>(lists.length, new Comparator<ListNode>() 
            @Override
            public int compare(ListNode o1, ListNode o2) 
                return o1.val - o2.val;
            
        );
        ListNode dummy = new ListNode(0);
        ListNode tail = dummy;
        for (ListNode node : lists) 
            if (node != null) 
                queue.add(node);
            
        
        while (!queue.isEmpty()) 
            tail.next = queue.poll();
            tail = tail.next;
            if (tail.next != null) 
                queue.add(tail.next);
            
        
        return dummy.next;
    

相似题目

• 21. 合并两个有序链表 Merge Two Sorted Lists
• 264. 丑数 II Ugly Number II

参考资料

• https://leetcode-cn.com/problems/merge-k-sorted-lists/
• https://leetcode.com/problems/merge-k-sorted-lists/