solution.py

"""
64 / 64 test cases passed.
Runtime: 156 ms
Memory Usage: 64 MB
"""
class ListNode:
    
    def __init__(self, val):
        self.val = val
        self.next = None


class MyLinkedList:

    def __init__(self):
        self.size = 0
        self.head = ListNode(0)


    def get(self, index: int) -> int:
        if index < 0 or index >= self.size:
            return -1
        cur = self.head
        for _ in range(index + 1):
            cur = cur.next
        return cur.val


    def addAtHead(self, val: int) -> None:
        self.addAtIndex(0, val)


    def addAtTail(self, val: int) -> None:
        self.addAtIndex(self.size, val)


    def addAtIndex(self, index: int, val: int) -> None:
        if index > self.size:
            return
        index = max(0, index)
        self.size += 1
        pred = self.head
        for _ in range(index):
            pred = pred.next
        to_add = ListNode(val)
        to_add.next = pred.next
        pred.next = to_add

    def deleteAtIndex(self, index: int) -> None:
        if index < 0 or index >= self.size:
            return
        self.size -= 1
        pred = self.head
        for _ in range(index):
            pred = pred.next
        pred.next = pred.next.next


# 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)