LC LINKEDLIST

简单

21. 合并两个有序链表：

#Method1 非递归
def mergetwosortedll(self,l1,l2):
	head = ListNode(None)
	res = head
	while l1 and l2:
		if l1.val<l2.val:
			head.next = ListNode(l1.val)
			l1 = l1.next
		else:
			head.next = ListNode(l2.val)
			l2 = l2.next
		head = head.next
	head.next = l1 if l1 else l2
	return res.next
#Method2 递归
def mergetwosortedll(self,l1,l2):
	if l1 is None:
		return l2
	elif l2 is None:
		return l1
	elif l1.val<l2.val:
		l1.next = self.mergetwosortell(l1.next,l2)
		return l1
	else:
		l2.next = self.mergetwosortedll(l1,l2.next)
		return l2

206. 反转链表

def reverselist(self,head):
	prev,cur=None,head
	while cur:
		cur.next,prev,cur=  prev,cur,cur.next
	return prev

剑指18. 删除链表节点

def deletenode(self,head,val):
	if head.val == val:
		head = head.next
	head2 = head
	while head2 and head2.next:
		if head2.val == val:
			head2.next = head2.next.next
		head2 = head2.next
	return head

141. 环形链表

def hasCycle(self,head):
	p2,p1 = head,head
	while p2 and p1 and p2.next:
		p2 = p2.next.next
		p1 = p1.next
		if p1==p2:
			return True
	return False

剑指22. 链表中倒数第k个节点

def getKthFromEnd(self,head,k):
	head1 = head
	for _ in range(k):
		head1 = head1.next
	res = head
	while head1:
		head1 = head1.next
		res = res.next
	return res

剑指52. 两个链表的第一个公共节点

def getIntesectionNode(self,headA,headB):
	node1, node2 = headA, headB
	while node1 != node2:
		node1 = node1.next if node1.next else node2
		node2 = node2.next if node2.next else node1
	return node1

中等

困难