mirror of
https://github.com/youngyangyang04/leetcode-master.git
synced 2025-07-08 08:50:15 +08:00
Update 0707.设计链表.md
This commit is contained in:
jianghongcheng
@ -485,172 +485,166 @@ class MyLinkedList {
|
||||
|
||||
Python：
|
||||
```python
|
||||
# 单链表
|
||||
class MyLinkedList1:
|
||||
|
||||
def __init__(self):
|
||||
self.dummy_head = Node()# 添加虚拟头指针，便于操作
|
||||
self.size = 0 # 设置一个链表长度的属性，便于后续操作，注意每次增和删的时候都要更新
|
||||
|
||||
def get(self, index):
|
||||
"""
|
||||
:type index: int
|
||||
:rtype: int
|
||||
"""
|
||||
if index < 0 or index >= self.size:
|
||||
return -1
|
||||
cur = self.dummy_head.next
|
||||
while(index):
|
||||
cur = cur.next
|
||||
index -= 1
|
||||
return cur.val
|
||||
|
||||
def addAtHead(self, val):
|
||||
"""
|
||||
:type val: int
|
||||
:rtype: None
|
||||
"""
|
||||
new_node = Node(val)
|
||||
new_node.next = self.dummy_head.next
|
||||
self.dummy_head.next = new_node
|
||||
self.size += 1
|
||||
|
||||
def addAtTail(self, val):
|
||||
"""
|
||||
:type val: int
|
||||
:rtype: None
|
||||
"""
|
||||
new_node = Node(val)
|
||||
cur = self.dummy_head
|
||||
while(cur.next):
|
||||
cur = cur.next
|
||||
cur.next = new_node
|
||||
self.size += 1
|
||||
|
||||
def addAtIndex(self, index, val):
|
||||
"""
|
||||
:type index: int
|
||||
:type val: int
|
||||
:rtype: None
|
||||
"""
|
||||
if index < 0:
|
||||
self.addAtHead(val)
|
||||
return
|
||||
elif index == self.size:
|
||||
self.addAtTail(val)
|
||||
return
|
||||
elif index > self.size:
|
||||
return
|
||||
|
||||
node = Node(val)
|
||||
cur = self.dummy_head
|
||||
while(index):
|
||||
cur = cur.next
|
||||
index -= 1
|
||||
node.next = cur.next
|
||||
cur.next = node
|
||||
self.size += 1
|
||||
|
||||
def deleteAtIndex(self, index):
|
||||
"""
|
||||
:type index: int
|
||||
:rtype: None
|
||||
"""
|
||||
if index < 0 or index >= self.size:
|
||||
return
|
||||
pre = self.dummy_head
|
||||
while(index):
|
||||
pre = pre.next
|
||||
index -= 1
|
||||
pre.next = pre.next.next
|
||||
self.size -= 1
|
||||
|
||||
# 双链表
|
||||
# 相对于单链表, Node新增了prev属性
|
||||
class Node:
|
||||
|
||||
def __init__(self, val=0, next = None, prev = None):
|
||||
（版本一）单链表法
|
||||
class ListNode:
|
||||
def __init__(self, val=0, next=None):
|
||||
self.val = val
|
||||
self.next = next
|
||||
self.prev = prev
|
||||
|
||||
|
||||
class MyLinkedList:
|
||||
|
||||
def __init__(self):
|
||||
self._head, self._tail = Node(0), Node(0) # 虚拟节点
|
||||
self._head.next, self._tail.prev = self._tail, self._head
|
||||
self._count = 0 # 添加的节点数
|
||||
|
||||
def _get_node(self, index: int) -> Node:
|
||||
# 当index小于_count//2时, 使用_head查找更快, 反之_tail更快
|
||||
if index >= self._count // 2:
|
||||
# 使用prev往前找
|
||||
node = self._tail
|
||||
for _ in range(self._count - index):
|
||||
node = node.prev
|
||||
else:
|
||||
# 使用next往后找
|
||||
node = self._head
|
||||
for _ in range(index + 1):
|
||||
node = node.next
|
||||
return node
|
||||
|
||||
|
||||
def _update(self, prev: Node, next: Node, val: int) -> None:
|
||||
"""
|
||||
更新节点
|
||||
:param prev: 相对于更新的前一个节点
|
||||
:param next: 相对于更新的后一个节点
|
||||
:param val: 要添加的节点值
|
||||
"""
|
||||
# 计数累加
|
||||
self._count += 1
|
||||
node = Node(val)
|
||||
prev.next, next.prev = node, node
|
||||
node.prev, node.next = prev, next
|
||||
self.dummy_head = ListNode()
|
||||
self.size = 0
|
||||
|
||||
def get(self, index: int) -> int:
|
||||
"""
|
||||
Get the value of the index-th node in the linked list. If the index is invalid, return -1.
|
||||
"""
|
||||
if 0 <= index < self._count:
|
||||
node = self._get_node(index)
|
||||
return node.val
|
||||
else:
|
||||
if index < 0 or index >= self.size:
|
||||
return -1
|
||||
|
||||
current = self.dummy_head.next
|
||||
for i in range(index):
|
||||
current = current.next
|
||||
|
||||
return current.val
|
||||
|
||||
def addAtHead(self, val: int) -> None:
|
||||
"""
|
||||
Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list.
|
||||
"""
|
||||
self._update(self._head, self._head.next, val)
|
||||
self.dummy_head.next = ListNode(val, self.dummy_head.next)
|
||||
self.size += 1
|
||||
|
||||
def addAtTail(self, val: int) -> None:
|
||||
"""
|
||||
Append a node of value val to the last element of the linked list.
|
||||
"""
|
||||
self._update(self._tail.prev, self._tail, val)
|
||||
current = self.dummy_head
|
||||
while current.next:
|
||||
current = current.next
|
||||
current.next = ListNode(val)
|
||||
self.size += 1
|
||||
|
||||
def addAtIndex(self, index: int, val: int) -> None:
|
||||
"""
|
||||
Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted.
|
||||
"""
|
||||
if index < 0:
|
||||
index = 0
|
||||
elif index > self._count:
|
||||
if index < 0 or index > self.size:
|
||||
return
|
||||
node = self._get_node(index)
|
||||
self._update(node.prev, node, val)
|
||||
|
||||
current = self.dummy_head
|
||||
for i in range(index):
|
||||
current = current.next
|
||||
current.next = ListNode(val, current.next)
|
||||
self.size += 1
|
||||
|
||||
def deleteAtIndex(self, index: int) -> None:
|
||||
"""
|
||||
Delete the index-th node in the linked list, if the index is valid.
|
||||
"""
|
||||
if 0 <= index < self._count:
|
||||
node = self._get_node(index)
|
||||
# 计数-1
|
||||
self._count -= 1
|
||||
node.prev.next, node.next.prev = node.next, node.prev
|
||||
if index < 0 or index >= self.size:
|
||||
return
|
||||
|
||||
current = self.dummy_head
|
||||
for i in range(index):
|
||||
current = current.next
|
||||
current.next = current.next.next
|
||||
self.size -= 1
|
||||
|
||||
|
||||
# Your MyLinkedList object will be instantiated and called as such:
|
||||
# obj = MyLinkedList()
|
||||
# param_1 = obj.get(index)
|
||||
# obj.addAtHead(val)
|
||||
# obj.addAtTail(val)
|
||||
# obj.addAtIndex(index,val)
|
||||
# obj.deleteAtIndex(index)
|
||||
```
|
||||
|
||||
|
||||
```python
|
||||
（版本二）双链表法
|
||||
class ListNode:
|
||||
def __init__(self, val=0, prev=None, next=None):
|
||||
self.val = val
|
||||
self.prev = prev
|
||||
self.next = next
|
||||
|
||||
class MyLinkedList:
|
||||
def __init__(self):
|
||||
self.head = None
|
||||
self.tail = None
|
||||
self.size = 0
|
||||
|
||||
def get(self, index: int) -> int:
|
||||
if index < 0 or index >= self.size:
|
||||
return -1
|
||||
|
||||
if index < self.size // 2:
|
||||
current = self.head
|
||||
for i in range(index):
|
||||
current = current.next
|
||||
else:
|
||||
current = self.tail
|
||||
for i in range(self.size - index - 1):
|
||||
current = current.prev
|
||||
|
||||
return current.val
|
||||
|
||||
def addAtHead(self, val: int) -> None:
|
||||
new_node = ListNode(val, None, self.head)
|
||||
if self.head:
|
||||
self.head.prev = new_node
|
||||
else:
|
||||
self.tail = new_node
|
||||
self.head = new_node
|
||||
self.size += 1
|
||||
|
||||
def addAtTail(self, val: int) -> None:
|
||||
new_node = ListNode(val, self.tail, None)
|
||||
if self.tail:
|
||||
self.tail.next = new_node
|
||||
else:
|
||||
self.head = new_node
|
||||
self.tail = new_node
|
||||
self.size += 1
|
||||
|
||||
def addAtIndex(self, index: int, val: int) -> None:
|
||||
if index < 0 or index > self.size:
|
||||
return
|
||||
|
||||
if index == 0:
|
||||
self.addAtHead(val)
|
||||
elif index == self.size:
|
||||
self.addAtTail(val)
|
||||
else:
|
||||
if index < self.size // 2:
|
||||
current = self.head
|
||||
for i in range(index - 1):
|
||||
current = current.next
|
||||
else:
|
||||
current = self.tail
|
||||
for i in range(self.size - index):
|
||||
current = current.prev
|
||||
new_node = ListNode(val, current, current.next)
|
||||
current.next.prev = new_node
|
||||
current.next = new_node
|
||||
self.size += 1
|
||||
|
||||
def deleteAtIndex(self, index: int) -> None:
|
||||
if index < 0 or index >= self.size:
|
||||
return
|
||||
|
||||
if index == 0:
|
||||
self.head = self.head.next
|
||||
if self.head:
|
||||
self.head.prev = None
|
||||
else:
|
||||
self.tail = None
|
||||
elif index == self.size - 1:
|
||||
self.tail = self.tail.prev
|
||||
if self.tail:
|
||||
self.tail.next = None
|
||||
else:
|
||||
self.head = None
|
||||
else:
|
||||
if index < self.size // 2:
|
||||
current = self.head
|
||||
for i in range(index):
|
||||
current = current.next
|
||||
else:
|
||||
current = self.tail
|
||||
for i in range(self.size - index - 1):
|
||||
current = current.prev
|
||||
current.prev.next = current.next
|
||||
current.next.prev = current.prev
|
||||
self.size -= 1
|
||||
|
||||
|
||||
|
||||
|
||||
Reference in New Issue
Block a user