Precourse-1 solution

[Simranb10]

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[super30admin]

The student has submitted three exercises implementing fundamental data structures in Java. Let me evaluate each one:

Exercise 1: Array-based Stack

• Correctness: The implementation correctly uses a fixed-size array with a top pointer to implement stack operations (push, pop, peek, isEmpty). The logic for handling overflow and underflow conditions is appropriate.
• Time Complexity: O(1) for all operations (push, pop, peek, isEmpty) - correctly identified.
• Space Complexity: O(1) for the stack itself (fixed MAX size), though the array is allocated upfront. The student's claim of O(1) is reasonable for the stack structure.
• Code Quality: The code is clean and readable. However, the MAX constant should be made private for encapsulation, and the array should be encapsulated within the class.

Exercise 2: Linked List-based Stack

• Correctness: The implementation correctly uses a linked list with a root pointer to implement stack operations. The push, pop, peek, and isEmpty methods work as expected.
• Time Complexity: O(1) for all operations - correctly identified.
• Space Complexity: O(n) - correctly identified. Each node consumes memory proportional to the number of elements.
• Code Quality: Good implementation with proper use of a static inner class for StackNode. The code is well-structured and follows good practices.

Exercise 3: Singly Linked List

• Correctness: The implementation correctly creates a singly linked list with insertion at the end and traversal/printing functionality.
• Time Complexity: O(n) for insertion (traversing to the end) - correctly identified.
• Space Complexity: O(n) - correctly identified.
• Code Quality: The code is well-structured with a static inner Node class. The insert method is correctly implemented. However, the printList method could be made static like the insert method for consistency.

General Observations:

1. All three exercises demonstrate a solid understanding of basic data structures.
2. The time and space complexity analyses are accurate.
3. The code follows Java conventions and is generally readable.
4. Minor improvements could include: adding proper access modifiers for encapsulation, adding javadoc comments, and handling edge cases more explicitly.