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merge-k-sorted-lists.py
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merge-k-sorted-lists.py
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# Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = None
import heapq
from typing import List, Tuple
class Solution:
def mergeKLists(self, lists: List[ListNode]) -> ListNode:
heap = []
count = 0
for node in lists:
if node is not None:
count += 1
heapq.heappush(heap, (node.val, count, node))
root = ListNode(None)
node = root
while True:
count += 1
if not heap:
break
min_node_val, c, min_node = heapq.heappop(heap)
node.next = min_node
node = node.next
if min_node.next is not None:
heapq.heappush(heap, (min_node.next.val, count, min_node.next))
# Definition for singly-linked list.
class ListNodeComparable:
def __init__(self, node: ListNode):
self.val = node.val
self.next = node.next
self.node = node
def __eq__(self, other: object) -> bool:
return self.val == other.val
def __lt__(self, other: object) -> bool:
return self.val < other.val
class Solution2:
def mergeKLists(self, lists: List[ListNode]) -> ListNode:
heap: List[ListNodeComparable] = []
head = ListNode()
for node in lists:
if node:
heapq.heappush(heap, ListNodeComparable(node))
node = head
while heap:
cur_node = heapq.heappop(heap)
if cur_node.next:
heapq.heappush(heap, ListNodeComparable(cur_node.next))
node.next = cur_node.node
node = node.next
return head.next