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design-linked-list.py
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design-linked-list.py
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# https://leetcode.com/problems/design-linked-list/
from typing import Optional
class Node:
def __init__(self, value: int, prev: Optional['Node'] = None, next: Optional['Node'] = None):
self.value = value
self.next = next
self.prev = prev
class MyLinkedList:
def __init__(self):
self.head = None
self.tail = None
self.size = 0
def getNodeByIndex(self, index: int) -> Node:
i = 0
node = self.head
while node:
if i == index:
return node
node = node.next
i += 1
def get(self, index: int) -> int:
if index < 0 or index >= self.size:
return -1
return self.getNodeByIndex(index).value
def addAtHead(self, val: int) -> None:
node = Node(val)
if self.head is None:
self.head = self.tail = node
else:
node.next = self.head
self.head.prev = node
self.head = node
self.size += 1
def addAtTail(self, val: int) -> None:
node = Node(val)
if self.head is None:
self.head = self.tail = node
else:
self.tail.next = node
node.prev = self.tail
self.tail = self.tail.next
self.size += 1
def addAtIndex(self, index: int, val: int) -> None:
if index < 0 or index > self.size:
return
if index == self.size:
self.addAtTail(val)
return
if index == 0:
self.addAtHead(val)
return
new = Node(val)
node = self.getNodeByIndex(index)
new.prev = node.prev
new.next = node
node.prev = new
new.prev.next = new
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
elif index == self.size - 1:
self.tail = self.tail.prev
self.tail.next = None
else:
node = self.getNodeByIndex(index)
node.prev.next = node.next
node.next.prev = node.prev
del node
self.size -= 1