题解 | #合并k个已排序的链表#

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    def mergeKLists(self , lists: List[ListNode]) -> ListNode:
        # write code here
        start = ListNode(-1)
        for head in lists:
            start = self.merge(start.next,head)
        
        return start.next

            
    def merge(self,head1,head2):
        start = ListNode(-1)
        cur = start
        while head1 and head2:
            if head1.val<=head2.val:
                cur.next = head1
                head1 = head1.next
            else:
                cur.next = head2
                head2 = head2.next
            cur = cur.next
        cur.next = head1 if head1 else head2
        return start