Complete Precourse-1

[paridhimalviya]

Exercise_1 : Implement Stack using Array.

Exercise_2 : Implement Stack using Linked List.

Exercise_3 : Implement Singly Linked List.

[super30admin]

The student has demonstrated a good understanding of data structures by implementing a linked list, a stack using an array, and a stack using a linked list. Here are some specific observations:

Strengths:

1. Correctness: The implementations appear to be functionally correct for basic operations (append, prepend, push, pop, etc.).
2. Modularity: The code is well-organized into separate files and classes for different data structures.
3. Documentation: There are helpful comments explaining the purpose of methods and classes.
4. Protocol Conformance: Proper use of CustomStringConvertible for printing the data structures.
5. Generics: Good use of generics to make the data structures type-safe and reusable.

Areas for Improvement:

1. Redundancy: There's some duplication between LinkedList and LLLinkedList/SinglyLinkedList. These could potentially be consolidated.
2. Error Handling: The code doesn't handle edge cases like popping from an empty stack or list (though it does check for emptiness).
3. Access Control: Some properties could be made private to better encapsulate the implementation details.
4. Naming: Some method names could be more consistent (e.g., push vs prepend, displayList vs description).
5. Testing: While there are example usages, more comprehensive test cases would be beneficial.
6. Time Complexity: The student should explicitly document the time complexity of each operation in comments.
7. Memory Management: In the linked list implementations, there's no explicit handling of memory management (though Swift uses ARC).

Time Complexity:

• Linked List operations (append/prepend): O(1)
• Stack operations (push/pop): O(1) for both array and linked list implementations
• Traversal: O(n)

Space Complexity:

• All implementations use O(n) space where n is the number of elements.

[super30admin]

The student's solution demonstrates a good understanding of linked lists and stacks, with implementations in Swift. Here's a detailed evaluation:

1. Correctness:

   • The LinkedList implementation correctly handles append and prepend operations, maintaining head and tail references.
   • The Stack implementation using an array is correct, with proper push, pop, and peek operations.
   • The LinkedListToStackAdapter correctly adapts a linked list to stack operations (push, pop, peek).
   • The SinglyLinkedList implementation correctly handles push and append operations.

2. Time Complexity:

   • LinkedList append/prepend: O(1)
   • Stack operations (push/pop/peek): O(1)
   • LinkedListToStackAdapter operations: O(1) for push/pop/peek
   • SinglyLinkedList push/append: O(1)

3. Space Complexity:

   • All implementations use O(n) space, where n is the number of elements, which is optimal for these data structures.

4. Code Quality:

   • Strengths:
     • Good use of generics (T) for type safety.
     • Proper separation of concerns with extensions for different functionalities.
     • Conformance to CustomStringConvertible for debugging.
     • Clear and consistent naming conventions.
   • Areas for Improvement:
     • Some duplicate code between LinkedList and LLLinkedList/SinglyLinkedList (could be consolidated).
     • The description property in LinkedListToStackAdapter could reuse the linked list's description.
     • Some optional unwrapping could be made safer (e.g., in displayList()).

5. Efficiency:

   • The implementations are generally efficient. One potential optimization:
     • The count property in LLLinkedList could be maintained as a stored property rather than computed each time.