def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
if not l1: return l2
if not l2: return l1
if l1.val <= l2.val:
l1.next = self.mergeTwoLists(l1.next, l2)
return l1
else:
l2.next = self.mergeTwoLists(l1, l2.next)
return l2
def reverseListNode(self, head: ListNode) -> ListNode:
if head.next is None:
return head
last = self.reverseListNode(head.next)
head.next.next = head
head.next = None
return last
def swapPairs(self, head: ListNode) -> ListNode:
if not head or not head.next:
return head
newHead = head.next
head.next = self.swapPairs(newHead.next)
newHead.next = head
return newHead
def reverseKGroup(self, head: ListNode, k: int) -> ListNode:
dummy = ListNode(0)
dummy.next = head
pre, end = dummy, dummy
while end.next:
# 取出待翻转的部分
i = 0
while i < k and end:
end = end.next
i += 1
if not end: break
# 断开链表
startNode = pre.next
nextNode = end.next
end.next = None
# 处理翻转
pre.next = self.reverse(startNode)
# startNode 转到翻转这部分节点的最后了
# 连接断开的链表
startNode.next = nextNode
# 挪动以进行下一组处理
pre = startNode
end = pre
return dummy.next
def reverseList(self, head: ListNode) -> ListNode:
if head.next is None:
return head
last = self.reverseList(head.next)
# 环形链表这里vscode没法展示
head.next.next = head
head.next = None
return last
def sortList(self, head: ListNode) -> ListNode:
res_ls = []
while head:
res_ls.append(head.val)
head = head.next
if len(res_ls) == 0:
return
res_ls.sort()
node = ListNode(res_ls[0])
new_head = node
for i in res_ls[1:]:
node.next = ListNode(i)
node = node.next
return new_head