【23. 合并K个排序链表】【困难】【优先队列/堆排序】

时间:2021-03-29 11:02:41

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。

示例:

输入:

[

1->4->5,

1->3->4,

2->6

]

输出: 1->1->2->3->4->4->5->6

/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode mergeKLists(ListNode[] lists) {
public class Solution {
public ListNode mergeKLists(List<ListNode> lists) {
Queue<ListNode> heap = new PriorityQueue(new Comparator<ListNode>(){
@Override public int compare(ListNode l1, ListNode l2) {
return l1.val - l2.val;
}
});
ListNode head = new ListNode(0), tail = head;
for (ListNode node : lists) if (node != null) heap.offer(node);
while (!heap.isEmpty()) {
tail.next = heap.poll();
tail = tail.next;
if (tail.next != null) heap.offer(tail.next);
}
return head.next;
}
}
}
}