Completed Pre Course-1

[PreethamRavula]

No description provided.

[super30admin]

The student has submitted three C++ files implementing fundamental data structures: a stack using an array, a stack using a linked list, and a singly linked list. Let me evaluate each:

Exercise_1.cpp (Array-based Stack):

• Correctness: The implementation is correct. Push, pop, peek, and isEmpty all work as expected with proper bounds checking.
• Time Complexity: O(1) for all operations - correctly stated.
• Space Complexity: O(1) for operations, O(n) for the array itself - the student states O(1) which is technically the auxiliary space per operation.
• Issues:
  • The MAX size of 1000 is a hardcoded limit, which is a known limitation of array-based stacks.
  • The peek() method has a return type of int but the declaration in the class is missing - actually it's there.
  • The peek() method should ideally be const since it doesn't modify state.
  • The isEmpty() method should also be const.
  • Using cout inside the stack methods is a side effect that violates separation of concerns - the stack should just return values and let the caller decide what to print.
  • The pop() method returns -1 on empty which is ambiguous (could be a valid value).
  • The class Stack s; in main is unusual - typically you'd just write Stack s;.

Exercise_2.cpp (Linked List-based Stack):

• Correctness: The implementation is correct. Memory is properly managed with delete temp in pop.
• Time Complexity: O(1) for all operations - correctly stated.
• Space Complexity: O(1) per operation, O(n) total - correctly stated.
• Issues:
  • The isEmpty function returns int (1 or 0) instead of bool - inconsistent with Exercise_1.
  • The peek and pop functions return -1 on empty which is ambiguous.
  • Using new without considering exceptions - though for this simple case it's fine.
  • The newNode function could be a constructor or use std::make_unique/std::make_shared for better memory management.
  • No destructor to clean up the entire stack - memory leak if not all nodes are popped.

Exercise_3.cpp (Singly Linked List):

• Correctness: The implementation is correct. Push, insertAfter, append, and printList all work correctly.
• Time Complexity: O(1) for push and insertAfter, O(n) for append and printList - correctly stated.
• Space Complexity: O(1) for all operations - correctly stated.
• Issues:
  • No destructor to clean up allocated nodes - memory leak.
  • The insertAfter function doesn't handle the case where prev_node is the last node (it actually does work correctly, but worth noting).
  • The append function could be optimized by maintaining a tail pointer for O(1) append.
  • No delete or remove function implemented.
  • The Node class members are public which breaks encapsulation - should be private with getters/setters or use struct if intentional.

General Code Quality Issues:

1. Unused includes: <vector> and <algorithm> are included but not used in any of the files.
2. Magic numbers: MAX = 1000 should be a named constant or configurable.
3. Mixed C-style and C++: Using NULL instead of nullptr.
4. No const correctness: Methods that don't modify state should be marked const.
5. No error handling: Using return values like -1 for errors is not ideal in C++ - should use exceptions or std::optional.
6. No destructors: Memory leaks possible if stack/list isn't fully drained.
7. Side effects in data structures: Using cout inside stack methods is bad practice.
8. Inconsistent return types: isEmpty returns int in Exercise_2 but bool in Exercise_1.

Strengths:

1. Good comments explaining each step.
2. Proper bounds checking in array-based stack.
3. Correct memory management in linked list stack (delete temp).
4. Clear separation of operations.
5. Time and space complexity documented.
6. Good use of pointer-to-pointer for head manipulation.

Overall, the implementations are functionally correct and demonstrate understanding of the basic data structures. However, there are several improvements that could be made in terms of C++ best practices, const correctness, memory management, and separation of concerns.