## Question

You are given an array of `k`

linked-lists `lists`

, each linked-list is sorted in ascending order.

*Merge all the linked-lists into one sorted linked-list and return it.*

**Example 1:**

Input:lists = [[1,4,5],[1,3,4],[2,6]]Output:[1,1,2,3,4,4,5,6]Explanation:The linked-lists are: [ 1->4->5, 1->3->4, 2->6 ] merging them into one sorted list: 1->1->2->3->4->4->5->6

**Example 2:**

Input:lists = []Output:[]

**Example 3:**

Input:lists = [[]]Output:[]

**Constraints:**

`k == lists.length`

`0 <= k <= 10`

^{4}`0 <= lists[i].length <= 500`

`-10`

^{4}<= lists[i][j] <= 10^{4}`lists[i]`

is sorted in**ascending order**.- The sum of
`lists[i].length`

will not exceed`10`

.^{4}

## Python Solution

from heapq import heappop,heappush,heapify class Solution: def mergeKLists(self, lists: List[ListNode]) -> ListNode: h = [] for l in lists: while l: heappush(h,l.val) l = l.next head = ListNode(0) head1 = head while h: head.next = ListNode(heappop(h)) head = head.next return head1.next