PreCourse 1 PR

[imran514]

No description provided.

[super30admin]

Let's evaluate each exercise separately:

Exercise_1.java (Array-based Stack):

1. Correctness: The stack implementation mostly works but has a few issues:
   • isEmpty() checks a.length which is always 1000 (MAX), so it's incorrect
   • push() should check top < MAX-1 since top starts at -1
   • peek() should check top >= 0 rather than a.length > 0
2. Time Complexity: Correctly noted as O(1) for all operations
3. Space Complexity: Correctly noted as O(n)
4. Code Quality: Good structure but needs better comments and edge case handling
5. Efficiency: The implementation is efficient for stack operations

Exercise_2.java (Linked List-based Stack):

1. Correctness: The implementation works but is inefficient:
   • push() and pop() are O(n) operations due to traversing the entire list
   • Typically stacks should have O(1) push/pop by adding/removing at head
2. Time Complexity: Incorrectly noted as O(n) - should be O(1) for proper stack
3. Space Complexity: Correctly noted as O(n)
4. Code Quality: Well-structured but inefficient implementation
5. Efficiency: Needs optimization by making operations O(1)

Exercise_3.java (Linked List):

1. Correctness: Implementation is correct
2. Time Complexity: Correctly noted as O(n) for insertion at end
3. Space Complexity: Correctly noted as O(n)
4. Code Quality: Good structure and readability
5. Efficiency: Standard implementation - could consider tail pointer for O(1) append

General improvements needed:

1. Fix isEmpty() implementation in Exercise_1
2. Optimize stack operations to O(1) in Exercise_2
3. Add more comments explaining logic
4. Handle edge cases more explicitly
5. Consider adding input validation