done Pre course exercise - 1

[yashhh-23]

No description provided.

[Copilot]

Pull request overview

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Implements three exercises for stack and linked list data structures in Java, filling in the previously stubbed methods.

Changes:

• Implements array-based Stack with push/pop/peek/isEmpty (Exercise_1).
• Implements linked-list-based stack with push/pop/peek/isEmpty and renames class to Exercise_2.
• Implements LinkedList Node constructor, insert, and printList methods (Exercise_3).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
Exercise_1.java	Implements array-based Stack operations and adds complexity comments.
Exercise_2.java	Implements linked-list stack operations; renames class to Exercise_2.
Exercise_3.java	Implements Node constructor, insert, and printList for linked list.

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[super30admin]

Exercise_1.java (Array-based Stack):

• ✅ Correctly implements stack operations with proper overflow/underflow checks
• ✅ Clean and readable code structure
• ✅ Time complexity comments are accurate (O(1) for all operations)
• ⚠️ Space complexity comment says O(n) but should specify it's O(MAX) = O(1000) fixed size
• ⚠️ Minor: Could use a more descriptive variable name than 'a' (e.g., 'stack')

Exercise_2.java (Linked List-based Stack):

• ✅ Excellent implementation of linked list-based stack
• ✅ Proper handling of empty stack conditions
• ✅ Clean separation of StackNode inner class
• ✅ Correct pointer manipulation in push/pop operations
• ✅ Time and space complexity comments are appropriate
• ⚠️ Minor: The class name "Exercise_2" is not descriptive; could be "LinkedListStack" or similar

Exercise_3.java (Singly Linked List):

• ✅ Correctly implements insertion at the end of linked list
• ✅ Proper traversal logic to find the last node
• ✅ Good use of static inner Node class
• ⚠️ Time complexity comment says O(n) but should clarify this is specifically for insert operation (which requires traversal)
• ⚠️ Space complexity comment says O(1) but this is misleading - the space complexity is O(n) for the linked list itself (excluding input), while the insert operation is O(n) time
• ⚠️ The printList method has inconsistent formatting (extra newline at the end)

General Observations:

• All three exercises demonstrate solid understanding of data structures
• Edge cases are handled appropriately (empty stack, overflow conditions)
• Code is well-commented with complexity analysis
• Good practice of separating driver code from implementation

Areas for Improvement:

• Complexity analysis comments could be more precise
• Class/file naming could be more descriptive
• Consider adding Javadoc-style comments for better documentation