class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class MyLinkedList(object):
def __init__(self):
self.null_node = ListNode()
self.size = 0
def get(self, index):
if index < 0 or index >= self.size:
return -1
currnt = self.null_node.next
for i in range(index):
currnt = currnt.next
return currnt.val
def addAtHead(self, val):
self.null_node.next = ListNode(val, self.null_node.next)
self.size += 1
def addAtTail(self, val):
current = self.null_node
while current.next:
current = current.next
current.next = ListNode(val)
self.size += 1
def addAtIndex(self, index, val):
if index<0 or index>self.size:
return
current = self.null_node
for i in range(index):
current = current.next
current.next = ListNode(val, current.next)
self.size += 1
def deleteAtIndex(self, index):
if index < 0 or index >= self.size:
return
current = self.null_node
for i in range(index):
current = current.next
current.next = current.next.next
self.size -= 1
