List Nodes - 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.

• What should the function return if the input n is zero?
  • The function should return an empty list since no nodes are requested to be listed.

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Traverse the linked list starting from the head, collecting the values of the first n nodes into a list, or all nodes if n exceeds the list's length.

1) Initialize an empty list `values` to store node values.
2) Start traversing the list from `head` with a counter initialized at 0.
3) Loop through the nodes, appending each node's value to `values` until either the end of the list is reached or `n` nodes have been processed.
4) Return the `values` list.

⚠️ Common Mistakes

• Not handling the case where n is greater than the number of nodes in the list, which should return all node values.
• Incorrectly setting loop conditions, leading to either excess or insufficient iterations.

I-mplement

def listify_first_n(head, n):
    # List to store the values of nodes
    values = []
    # Start from the head node
    current = head
    # Counter to track the number of nodes processed
    count = 0
    # Loop until 'current' is not None and 'count' is less than 'n'
    while current is not None and count < n:
        # Append current node's value to the list
        values.append(current.value)
        # Move to the next node
        current = current.next
        # Increment the counter
        count += 1
    # Return the list of collected values
    return values