206. Reverse Linked List

Posted on Oct 18, 2023

# O(n) time || O(1) space
def reverse_list(self, head: Optional[ListNode]) -> Optional[ListNode]:
    prev, curr = None, head
    while curr:
        curr.next, prev, curr = prev, curr, curr.next

    return prev

traverse linked list using curr pointer. relink curr.next to prev each step on iteration.
return the prev as head of reversed list