Print Backwards - 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 do if the tail is None (i.e., the list is empty)?
  • If the list is empty, the function should print an empty string or handle the case gracefully without errors.

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Traverse the doubly linked list starting from the tail, collect values, and print them in reverse order.

1) Start at the `tail` node of the doubly linked list.
2) Traverse backwards using the `prev` attribute of each node to collect the values.
3) Store each value in a list.
4) Join the list of values into a string with spaces and print the result.

⚠️ Common Mistakes

• Forgetting to convert node values to strings before joining them, which could raise a TypeError if the values are not strings.
• Not handling the empty list case, leading to potential errors or incorrect outputs.

I-mplement

def print_reverse(tail):
    values = []
    current = tail
    while current:
        values.append(str(current.value))
        current = current.prev
    print(" ".join(values))