chore: Completed precourse-1

[pkmaster21]

No description provided.

[super30admin]

Let's evaluate each file one by one.

Exercise_1.py:
This implements a stack using a list. The implementation is straightforward and correct for basic stack operations. However, there are a few points to note:

• The isEmpty method could be simplified to return len(self.arr) == 0.
• The peek method should handle the case when the stack is empty to avoid an IndexError. Currently, it will crash if called on an empty stack.
• The pop method should also handle the case when the stack is empty. Currently, it will raise an IndexError with "pop from empty list".
• The time complexity comments are accurate: all operations are O(1) except when the list needs to resize (which is amortized O(1)), and space complexity is O(n).
• The code quality is good: it's readable and well-commented.

Exercise_2.py:
This also implements a stack using a list, but with a command-line interface. However, there's a major issue: the class is named Stack, but it uses self.arr (which is a list) and the methods are implemented using list operations. This is similar to Exercise_1, but the problem might have intended to use a linked list (given the Node class defined but not used). The Node class is defined but never utilized in the Stack class. This seems like a mistake.

• The Stack class should probably be implemented using the Node class to form a linked list, but here it's using a list. This might not meet the problem requirements if the goal was to implement a stack with linked list.
• The time and space complexity are correctly stated.
• The code handles empty stack in pop by returning None, which is good.
• The command-line interface is implemented correctly.

Exercise_3.py:
This implements a singly linked list with append, find, and remove operations.

• The append method is O(n) as it traverses to the end, which is correct.
• The find method is O(n) and returns the node or None, which is correct.
• The remove method has an issue: if the list is empty, accessing self.head.data will cause an AttributeError (NoneType has no attribute 'data'). Also, if the key is not found, it does nothing (which is acceptable), but it should handle the empty list case.
• The remove method should check if the list is empty first. Also, it sets both current and prev to self.head initially, which might lead to issues. Typically, we initialize prev = None and current = self.head, then traverse.
• The code quality is good, but the removal logic could be improved for clarity and correctness.

General feedback:

• The student has a good understanding of basic data structures but needs to be careful with edge cases (like empty stacks/lists).
• For Exercise_2, there's a disconnect: the Node class is defined but not used. This might be a requirement of the problem to implement a linked list-based stack.
• The time and space complexity analysis is generally correct.