PreCourse-1

[jose-rafael-marcano]

xercise_1 : Implement Stack using Array.

Exercise_2 : Implement Stack using Linked List.

Exercise_3 : Implement Singly Linked List.

[super30admin]

1. Correctness:

   • Exercise_1 (Stack using array): The implementation correctly handles push, pop, and peek operations. The isEmpty check is correct. However, the peek() method has a bug - it should return the element at top-1 since top points to the next available position.
   • Exercise_2 (Stack using linked list): The implementation is mostly correct, but the peek() method doesn't handle the empty stack case, which could lead to NullPointerException.
   • Exercise_3 (Linked List): The implementation is correct for insertion and printing operations.

2. Time Complexity:

   • Exercise_1: All operations (push, pop, peek, isEmpty) are O(1).
   • Exercise_2: All operations are O(1) except for potential memory allocation time.
   • Exercise_3: Insertion is O(n) as it traverses to the end, printList is O(n).

3. Space Complexity:

   • Exercise_1: O(n) where n is MAX (1000).
   • Exercise_2: O(n) where n is number of elements.
   • Exercise_3: O(n) where n is number of elements.

4. Code Quality:

   • Generally good structure and readability.
   • Some improvements needed:
     • Missing comments about time/space complexity at the top of each file as requested.
     • In Exercise_1, the peek() method has a bug as mentioned.
     • In Exercise_2, peek() should handle empty stack case.
     • In Exercise_3, the insert method could be made non-static for better object-oriented design.

5. Efficiency:

   • Exercise_1: Setting popped elements to Integer.MIN_VALUE is unnecessary.
   • Exercise_2: No major inefficiencies.
   • Exercise_3: Could maintain a tail pointer to make insertions O(1).