Linked List Length - codepath/compsci_guides GitHub Wiki

Unit 5 Session 2 (Click for link to problem statements)

U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

• How does the function behave if the linked list is empty (head is None)?
  • The function should return 0, indicating that there are no nodes in the list.

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Traverse the linked list from the head to the end, counting each node until no more nodes are left.

1) Initialize a counter `count` to zero to track the number of nodes.
2) Start at the `head` and traverse the list using a loop.
3) For each node encountered, increment the `count`.
4) Once the end of the list is reached (`current` becomes `None`), return the `count`.

⚠️ Common Mistakes

• Forgetting to increment the count within the loop, which could result in returning zero regardless of the list's length.
• Mishandling the end condition where the list is empty, which should still correctly return 0.

I-mplement

def ll_length(head):
  count = 0

  current = head
  while current:
    count += 1
    current = current.next
  return count