Implemented Stack and LinkedList exercises (Pre-course 1)

[ratnadeepnayak]

Completed preCourse 1 exercise

[super30admin]

Let me evaluate each exercise separately:

Exercise_1.js (Stack implementation using array):

1. Correctness: The implementation has some issues. The isEmpty() method incorrectly checks array length instead of using the 'top' variable. The push() method doesn't increment 'top' or check for stack overflow.
2. Time Complexity:
   • push(): O(1) (correct)
   • pop(): O(1) (correct)
   • isEmpty(): O(1) (but implementation is wrong)
3. Space Complexity: O(n) (correct)
4. Code Quality: The code is readable but inconsistent in using the 'top' variable. The MAX constant is defined but not used properly.
5. Efficiency: Should use 'top' properly to track stack state instead of relying on array length.

Exercise_2.js (Stack implementation using linked list):

1. Correctness: The implementation is mostly correct. The isEmpty(), push(), pop(), and peek() methods work as expected.
2. Time Complexity:
   • All operations are O(1) (correct)
3. Space Complexity: O(n) (correct)
4. Code Quality: Good structure and readability. The static stackNode class is a nice touch.
5. Efficiency: No major improvements needed.

Exercise_3.js (Linked List implementation):

1. Correctness: The implementation has a bug - the insert method has duplicate traversal code and returns an unused value. The printList method works correctly.
2. Time Complexity:
   • insert(): O(n) (correct but inefficient due to duplicate traversal)
   • printList(): O(n) (correct)
3. Space Complexity: O(n) (correct)
4. Code Quality: The code is readable but has redundant logic in insert(). The return value from insert() is unused.
5. Efficiency: Remove duplicate traversal in insert() and consider making it chainable.

Common areas for improvement:

1. Add comments about time/space complexity at the top of each file as requested
2. Handle edge cases better (e.g., stack overflow in array implementation)
3. Remove redundant code (especially in Exercise_3.js)
4. Be consistent in using class variables (e.g., 'top' in array implementation)