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

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;
    }
    @Override
    public String toString() {
        return val + "->" + next;
    }
}

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/