Daisy Chain - codepath/compsci_guides GitHub Wiki

TIP102 Unit 5 Session 1 Advanced (Click for link to problem statements)

Problem Highlights

  • 💡 Difficulty: Easy
  • ⏰ Time to complete: 5-10 mins
  • 🛠️ Topics: Linked Lists, Node Connections

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 happens if the nodes are not linked correctly?
    • The linked list will not follow the intended sequence, and the output of the linked list will be incorrect.
HAPPY CASE
Input: nodes = Node("Daisy") -> Node("Peach") -> Node("Luigi") -> Node("Mario")
Output: "Daisy -> Peach -> Luigi -> Mario"
Explanation: The nodes are correctly linked to form the desired sequence.

EDGE CASE
Input: nodes = Node("Daisy"), Node("Peach"), Node("Luigi"), Node("Mario") (but not linked)
Output: "Daisy"
Explanation: Since the nodes are not linked, only the first node "Daisy" will be printed.

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 connection problems, we want to consider the following approaches:

  • Linking nodes sequentially using the next pointer.

3: P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Connect the nodes in the order daisy -> peach -> luigi -> mario by setting each node's next pointer to the following node.

1) Set the `next` pointer of `daisy` to `peach`.
2) Set the `next` pointer of `peach` to `luigi`.
3) Set the `next` pointer of `luigi` to `mario`.
4) Print the linked list starting from `daisy` to verify the connections.

⚠️ Common Mistakes

  • Forgetting to link all nodes, which results in an incomplete or incorrect sequence.
  • Misordering the links, leading to an unintended sequence.

4: I-mplement

Implement the code to solve the algorithm.

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

# For testing
def print_linked_list(head):
    current = head
    while current:
        print(current.value, end=" -> " if current.next else "\n")
        current = current.next

daisy = Node("Daisy")
peach = Node("Peach")
luigi = Node("Luigi")
mario = Node("Mario")

# Link the nodes to form the linked list
daisy.next = peach
peach.next = luigi
luigi.next = mario

5: R-eview

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

  • Verify the order of the linked list by printing it after the nodes are linked.

Example:

print_linked_list(daisy)  # Expected Output: "Daisy -> Peach -> Luigi -> Mario"

6: E-valuate

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

Time Complexity:

  • O(1), since we are performing a fixed number of operations to link the nodes.

Space Complexity:

  • O(1), as no additional space is required beyond the original nodes. This solution efficiently links the nodes in a singly linked list with minimal complexity.