delete_nth_node
delete_nth_node.py 源码
# 删除链表倒数第N个节点
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution:
# 先计数，再删除
def removeNthFromEnd_1(self, head: ListNode, n: int) -> ListNode:
def length(node: ListNode) -> int:
k = 0
while node:
k, node = k + 1, node.next
return k
dummy = ListNode(0, head)
length = length(head)
cur = dummy
for _ in range(1, length - n + 1):
cur = cur.next
cur.next = cur.next.next
return dummy.next
# 快慢指针，一次遍历
def removeNthFromEnd_2(self, head: ListNode, n: int) -> ListNode:
dummy = ListNode(0, head)
slow, fast = dummy, head
for _ in range(n):
fast = fast.next
while fast:
slow, fast = slow.next, fast.next
slow.next = slow.next.next
return dummy.next
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