Introduction
When learning Data Structures and Algorithms (DSA), many developers struggle to find real-world applications for the concepts they study. One such fundamental data structure is the Stack. While it may seem theoretical at first, stacks have many practical applications, including implementing Undo and Redo functionality in apps.
In this article, we will explore the Stack data structure and see how it can be used to implement Undo/Redo in a simple Todo App.
What is a Stack?
A Stack is a linear data structure that follows the Last In, First Out (LIFO) principle. This means that the last item added to the stack is the first one to be removed.
Key Operations of a Stack:
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Push: Adds an item to the top of the stack. -
Pop: Removes the top item from the stack. -
Peek (Top): Returns the top item without removing it. -
isEmpty: Checks if the stack is empty.
Implementing Undo/Redo in a Todo App
Application Features:
Our Todo App will have the following features:
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Text Field: Allows users to enter and add tasks. -
Undo Button: Removes the last task and moves it to the redo stack. -
Redo Button: Restores the last undone task from the redo stack. -
Show Stacks Button: Displays the contents of both the Main Stack (tasks) and the Redo Stack.
Stack Implementation in the Todo App:
In this implementation, we use two stacks:
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Main Stack: Stores the active tasks. -
Redo Stack: Stores the undone tasks.
How Undo/Redo Works:
When a task is added, it is pushed onto the Main Stack.
When the Undo button is clicked, the top task is popped from the Main Stack and pushed onto the Redo Stack.
When the Redo button is clicked, the top task is popped from the Redo Stack and pushed back onto the Main Stack.
Clicking Show Stack will display both stacks, highlighting the top item with a darker shade.
Code:- GitHub Link
Conclusion
Stacks are a fundamental data structure with many real-world applications. Implementing Undo and Redo functionality in a Todo App is a practical way to understand stacks in action. By visualizing how tasks move between stacks, developers can better grasp the LIFO concept and its importance in application development.
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