53. Undo/Redo for Text Editor

Implement a TextEditor class that supports INSERT, DELETE, UNDO, and REDO operations. The editor should maintain a history of operations using a stack-based approach.

Requirements

1. Basic Operations

• INSERT(text, position): Insert text at a given position
• DELETE(position, length): Delete characters starting at position
• UNDO(): Undo the last operation
• REDO(): Redo the last undone operation
• getText(): Return the current text content

Example Usage

const editor = new TextEditor();

editor.insert('Hello', 0);        // text = 'Hello'
editor.insert(' World', 5);      // text = 'Hello World'
editor.delete(5, 6);              // text = 'Hello'
editor.undo();                    // text = 'Hello World'
editor.undo();                    // text = 'Hello'
editor.redo();                    // text = 'Hello World'

Key Concepts

• Use two stacks: one for undo operations, one for redo operations
• Store operations as objects with type and necessary data
• When performing INSERT/DELETE, push to undo stack and clear redo stack
• When UNDO, pop from undo stack, apply inverse operation, push to redo stack
• When REDO, pop from redo stack, apply operation, push to undo stack