解法一：直接合并后排序
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
def mergeKLists(lists):
all_nodes = []
for linked_list in lists:
while linked_list:
all_nodes.append(linked_list.val)
linked_list = linked_list.next
all_nodes.sort()
dummy = ListNode(0)
current = dummy
for val in all_nodes:
current.next = ListNode(val)
current = current.next
return dummy.next
解法二：使用优先队列（堆）
import heapq
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
def mergeKLists(lists):
heap = []
for i, linked_list in enumerate(lists):
if linked_list:
heapq.heappush(heap, (linked_list.val, i, linked_list))
dummy = ListNode(0)
current = dummy
while heap:
val, index, node = heapq.heappop(heap)
current.next = ListNode(val)
current = current.next
node = node.next
if node:
heapq.heappush(heap, (node.val, index, node))
return dummy.next
