Linked List Front Back Pointers¶
Table of Contents¶
- 19. Remove Nth Node From End of List (Medium)
- 61. Rotate List (Medium)
- 1721. Swapping Nodes in a Linked List (Medium)
- 1474. Delete N Nodes After M Nodes of a Linked List (Easy) 👑
19. Remove Nth Node From End of List¶
"""
- Given the `head` of a linked list, remove the `n-th` node from the end of the list and return its head.
"""
from typing import Optional
from leetpattern.utils import ListNode, list_from_array, list_to_array
# Linked List
def removeNthFromEnd(head: Optional[ListNode], n: int) -> Optional[ListNode]:
dummy = ListNode(0, head)
fast, slow = dummy, dummy
for _ in range(n):
fast = fast.next
while fast.next:
fast = fast.next
slow = slow.next
slow.next = slow.next.next
return dummy.next
def test_removeNthFromEnd() -> None:
head = list_from_array([1, 2, 3, 4, 5])
assert (list_to_array(removeNthFromEnd(head, 2))) == [1, 2, 3, 5]
61. Rotate List¶
1721. Swapping Nodes in a Linked List¶
1474. Delete N Nodes After M Nodes of a Linked List¶
from typing import Optional
from leetpattern.utils import ListNode
# Linked List
def deleteNodes(
head: Optional[ListNode], m: int, n: int
) -> Optional[ListNode]:
dummy = ListNode(0, head)
cur = dummy
while cur.next:
for _ in range(m):
if not cur.next:
break
cur = cur.next
for _ in range(n):
if not cur.next:
break
cur.next = cur.next.next
return dummy.next
if __name__ == "__main__":
head = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
m = 2
n = 3
head = list_from_array(head)
print(head)
# 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 -> 9 -> 10 -> 11 -> 12 -> 13
head = deleteNodes(head, m, n)
print(head)
# 1 -> 2 -> 6 -> 7 -> 11 -> 12