Merge k Sorted Lists

题目描述

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.

题目解答

解题思路

创建一个优先级队列，每次弹出最小的元素，弹入最小元素的下一个元素，然后不断地迭代，直到队列为空。

代码实现

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; } * } */public class Solution {    public ListNode mergeKLists(ListNode[] lists){        if(lists.length == 0)            return null;        PriorityQueue<ListNode> queue = new PriorityQueue<>(new Comparator<ListNode>() {            @Override            public int compare(ListNode o1, ListNode o2) {                return o1.val - o2.val;            }        });        for(ListNode temp : lists){            if(temp != null)                queue.add(temp);        }        ListNode dummy = new ListNode(0);        ListNode cur = dummy;        dummy.next = null;        while(!queue.isEmpty()){            ListNode min = queue.poll();            cur.next = min;            cur = min;            if(min.next != null)                queue.add(min.next);        }        return dummy.next;    }}