Here is my Brute Force solution with Python. However, OJ indicated time limit error when the input is [[]]. I was expecting the Brute Force method would exceed the time limit, but definitely not in this case. Is there anything wrong with my code?

```
class Solution:
# @param {ListNode[]} lists
# @return {ListNode}
def mergeKLists(self, lists):
k = len(lists)
dummy = ListNode(None)
i = 0
curr_head = dummy
# merge the k lists one by one
while i < k:
head = dummy
p = curr_head
q = lists[i]
# merge two lists
while p is not None and q is not None:
if p.val <= q.val:
head.next = p
p = p.next
else:
head.next = q
q = q.next
head = head.next
if p is not None:
head.next = p
if q is not None:
head.next = q
curr_head = dummy.next
i += 1
return dummy.next
```