707. Design Linked List

https://leetcode.com/problems/design-linked-list/
Python

class ListNode:
    def __init__(self, val, nxt=None, pre=None):
        self.val = val
        self.next = nxt
        self.pre = pre

class MyLinkedList:
    def __init__(self):
        self.size = 0
        self.head = ListNode(val=None)
        self.tail = ListNode(val=None)
        self.head.next = self.tail
        self.tail.pre = self.head

    def get(self, index: int) -> int:
        if index < 0 or index >= self.size:
            return -1

        c = self.head
        while c:
            print(c.val, end=", ")
            c = c.next
        cur = self.head
        for i in range(index+1):
            cur = cur.next
        return cur.val

    def addAtHead(self, val: int) -> None:
        pre, succ = self.head, self.head.next
        new_node = ListNode(
            val=val,
            nxt=self.head.next,
            pre=self.head
        )

        self.head.next.pre = new_node
        self.head.next = new_node
        self.size += 1

    def addAtTail(self, val: int) -> None:
        new_node = ListNode(
            val=val,
            nxt=self.tail,
            pre=self.tail.pre
        )
        self.tail.pre.next = new_node
        self.tail.pre = new_node
        self.size += 1

    def addAtIndex(self, index: int, val: int) -> None:
        if index > self.size:
            return

        # To sure index not be native number
        index = max(0, index)

        cur = self.head
        for _ in range(index):
            cur = cur.next

        new_node = ListNode(
            val = val,
            nxt=cur.next,
            pre=cur
        )
        cur.next.pre = new_node
        cur.next = new_node
        self.size += 1

    def deleteAtIndex(self, index: int) -> None:
        if index < 0 or index >= self.size:
            return

        cur = self.head
        for _ in range(index):
            cur = cur.next
        succ = cur.next.next

        cur.next = succ
        succ.pre = cur
        self.size -= 1
Python​

Python
