# [Solved] 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. ## 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 <= 104`
• `0 <= lists[i].length <= 500`
• `-104 <= lists[i][j] <= 104`
• `lists[i]` is sorted in ascending order.
• The sum of `lists[i].length` will not exceed `104`.

## 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