LeetCode/707. Design Linked List at master · wongbenshing/LeetCode · GitHub

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class Node:
    def __init__(self, val=None):
        self.val = val
        self.next = None

class MyLinkedList:

    def __init__(self):
        self.head = Node()
        """
        Initialize your data structure here.
        """

    def out(self):
        cur = self.head
        ans = []
        while cur:
            ans.append(cur.val)
            cur = cur.next
        print(ans)

    def get(self, index: 'int') -> 'int':
        count = 0
        cur = self.head
        while cur.next:
            if count == index:
                return cur.next.val
            else:
                cur = cur.next
                count += 1
        return -1
        """
        Get the value of the index-th node in the linked list. If the index is invalid, return -1.
        """


    def addAtHead(self, val: 'int') -> 'None':
        add = Node(val)
        pre = self.head.next if self.head.next else None
        add.next = pre
        self.head.next = add
        #self.out()
        """
        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.
        """


    def addAtTail(self, val: 'int') -> 'None':
        add = Node(val)
        cur = self.head.next if self.head.next else self.head
        while cur.next:
            cur = cur.next
        cur.next = add
        #self.out()
        """
        Append a node of value val to the last element of the linked list.
        """


    def addAtIndex(self, index: 'int', val: 'int') -> 'None':
        count = 0
        cur = self.head
        while cur.next:
            if count == index:
                add = Node(val)
                temp = cur.next
                add.next = temp
                cur.next = add
                #self.out()
                return
            else:
                count += 1
                cur = cur.next
        if index == count:
            cur.next = Node(val)
        #self.out()
        """
        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.
        """


    def deleteAtIndex(self, index: 'int') -> 'None':
        count = 0
        cur = self.head
        while cur.next:
            if count == index:
                cur.next = cur.next.next
                #self.out()
                return
            else:
                count += 1
                cur = cur.next
        if count == index:
            cur = None
        #self.out()
        """
        Delete the index-th node in the linked list, if the index is valid.
        """


# 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)