from collections import deque
class Solution:
def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
"""
this method takes O(N) space complexity
"""
dq = deque()
node = head
while node:
dq.append(node)
node = node.next
if n == len(dq):
if len(dq) == 1:
return None
else:
return dq[1]
elif n == 1:
dq[-2].next = None
return dq[0]
else:
dq[-n - 1].next = dq[-n + 1]
return dq[0]
# ans = Solution().removeNthFromEnd(ListNode.parse([1,2,3,4,5]), 2)
ans = Solution().removeNthFromEnd(ListNode.parse([1, 2]), 1)
print(ans)
print(ans.serialize())
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution:
def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
sentinel = ListNode(0, None)
node = sentinel
carry = 0
while l1 or l2 or carry:
s = carry
if l1:
s += l1.val
l1 = l1.next
if l2:
s += l2.val
l2 = l2.next
carry = s // 10
node.next = ListNode(s % 10, None)
node = node.next
return sentinel.next
a = ListNode.parse([9, 9, 9, 9, 9, 9, 9])
b = ListNode.parse([9, 9, 9, 9])
ans = Solution().addTwoNumbers(a, b)
print(ans.serialize())
