Wow in #leetcode we can #patch classes:
ListNode.__lt__ = lambda self, other: self.val < other.val
This is good for simpler support of heap - by providing the object only - without the index and value.
Full:
import heapq
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
ListNode.__lt__ = lambda self, other: self.val < other.val
class Solution:
def mergeKLists(self, lists: List[Optional[ListNode]]) -> Optional[ListNode]:
heap = []
for node in lists:
if node:
heapq.heappush(heap, node)
head: List[ListNode] = ListNode()
tail = head
while heap:
node = heapq.heappop(heap)
tail.next = node
tail = node
if node.next:
heapq.heappush(heap, node.next)
return head.next
👍 1