Building a Playlist

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TIP102 Unit 6 Session 1 Standard (Click for link to problem statements)

Problem Highlights

• 💡 Difficulty: Easy
• ⏰ Time to complete: 10-15 mins
• 🛠️ Topics: Linked Lists

1: U-nderstand

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

• Established a set (2-3) of test cases to verify their own solution later.
• Established a set (1-2) of edge cases to verify their solution handles complexities.
• Have fully understood the problem and have no clarifying questions.
• Have you verified any Time/Space Constraints for this problem?

• What does the problem ask for?
  • The problem asks for creating a linked list using multiple lines instead of a single nested constructor statement.
• What is the structure of the linked list?
  • The linked list consists of nodes, each containing a song title and a reference to the next node.

HAPPY CASE
Input: top_hits_2010s = SongNode("Uptown Funk", SongNode("Dynamite", SongNode("Telephone")))
Output: Uptown Funk -> Dynamite -> Telephone
Explanation: The output is the linked list where each node points to the next in sequence.

EDGE CASE
Input: top_hits_2010s = None
Output: (no output)
Explanation: An empty list (no nodes) should simply print nothing.

2: M-atch

Match what this problem looks like to known categories of problems, e.g. Linked List or Dynamic Programming, and strategies or patterns in those categories.

For Linked List problems, we want to consider the following approaches:

• Constructing a linked list: The main task is to create a linked list by properly linking nodes together.

3: P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: We will break down the construction of the linked list into multiple lines where each node is created separately and linked to the next node.

1) Create the last node (Telephone) without linking it to any other node.
2) Create the second node (Dynamite) and link it to the last node (Telephone).
3) Create the first node (Uptown Funk) and link it to the second node (Dynamite).
4) The first node (Uptown Funk) will now serve as the head of the linked list.

⚠️ Common Mistakes

• Forgetting to link nodes correctly could lead to broken or circular linked lists.
• Not initializing the next node properly might result in errors.

4: I-mplement

Implement the code to solve the algorithm.

class Node:
    def __init__(self, value, next=None):
        self.value = value
        self.next = next

node3 = SongNode("Telephone")
node2 = SongNode("Dynamite", node3)
top_hits_2010s = SongNode("Uptown Funk", node2)

5: R-eview

Review the code by running specific example(s) and recording values (watchlist) of your code's variables along the way.

• Example: Start with top_hits_2010s and trace through to ensure each SongNode is linked correctly.
• Confirm that top_hits_2010s.next points to Dynamite and Dynamite.next points to Telephone.

6: E-valuate

Evaluate the performance of your algorithm and state any strong/weak or future potential work.

Assume N represents the number of nodes in the linked list.

• Time Complexity: O(N) because creating and linking the nodes requires a linear traversal through the list.
• Space Complexity: O(1) because we are not using any extra space beyond the list itself.