Use The Code From The Book And Notes To Implement A

Use The Code From The Book And From My Notes To Implement A Stack Ad

Use the code from the book (and from my notes) to implement a Stack ADT using a linked list. Use this Stack to implement Dijkstra’s Two-Stack Algorithm for expression evaluation. This code is also given in the book and in my notes. You will need to change this code so that the algorithm is in a separate method for the evaluation. That is, read the input into a String variable that you pass to your method for evaluation. To this code, add Junit test to test the Stack methods and to test the evaluate method.

Paper For Above instruction

Introduction

The implementation of fundamental data structures such as stacks is crucial in computer science due to their widespread application in algorithms and problem-solving scenarios. In particular, the Stack Abstract Data Type (ADT) can be effectively implemented using linked lists, facilitating dynamic memory management and efficient operations. This paper discusses the process of implementing a Stack ADT via a linked list, utilizing code from standard textbooks and instructor notes, and applying this implementation to realize Dijkstra’s Two-Stack Algorithm for expression evaluation. Additionally, the paper emphasizes the importance of modular design by encapsulating the algorithm within a separate method that accepts input expressions as strings. To ensure robustness and correctness, unit testing with JUnit is incorporated to test both the Stack methods and the expression evaluation method.

Implementation of Stack ADT Using a Linked List

The Stack ADT, characterized by the Last-In-First-Out (LIFO) principle, relies on core operations such as push, pop, peek, and isEmpty. Using a linked list allows these operations to be performed efficiently without the need for resizing or shifting elements, as in array-based implementations. The linked list implementation involves creating a Node class that contains the data and a reference to the next node. The Stack class maintains a reference to the top node, and operations are defined as follows:

• push: Creates a new node and sets it as the new top, linking it to the previous top.
• pop: Removes and returns the data from the top node, updating the top reference.
• peek: Returns the data at the top node without removing it.
• isEmpty: Checks if the top reference is null.

The code, sourced from standard textbooks and instructor notes, exemplifies this approach with clear class structures and methods, emphasizing encapsulation and clean code practices.

Applying the Stack to Dijkstra’s Two-Stack Algorithm

Dijkstra’s Two-Stack Algorithm for expression evaluation involves maintaining two stacks: one for operators and one for operands. When an expression string is input, it is parsed token by token. Numbers are pushed onto the value stack, and operators onto the operator stack. When a closing parenthesis or operator precedence dictates, operations are performed by popping operators and operands, applying the operations, and pushing the result back onto the value stack. The implementation requires careful handling of input parsing, operator precedence, and parenthesis management.

To enhance modularity, the algorithm is encapsulated within a dedicated method that accepts a string expression as input. This method is responsible for parsing the string, managing stacks, and returning the final evaluated value. The main program reads input expressions, passes them to this method, and displays results.

Enhancement with JUnit Testing

Testing ensures the correctness and robustness of the implementation. JUnit tests are written to verify the Stack methods such as push, pop, peek, and isEmpty, ensuring they conform to expected behaviors. Furthermore, tests are created for the expression evaluation method, comparing known input expressions with their expected results. These tests help identify bugs, validate algorithm correctness, and facilitate future modifications.

Conclusion

Implementing a Stack ADT using a linked list provides a flexible and efficient data structure suitable for various algorithms. The application of the stack in Dijkstra’s Two-Stack Algorithm demonstrates its practical utility in expression evaluation. Encapsulating the algorithm within a separate method enhances code clarity and reusability. Incorporating JUnit tests ensures the reliability of both stack operations and the evaluation logic, promoting robust software development practices.

References

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