Implement a text document with undo/redo based on this Python skeleton: class Operation: class InsertAtEndOperation(Operation): def __init__(self, chars_to_insert: str): self.chars_to_insert = chars_to_insert class DeleteFromEndOperation(Operation): def __init__(self, num_chars_to_delete: int): self.num_chars_to_delete = num_chars_to_delete class TextDocument: def __init__(self) -> None: def apply_operation(self, op: Operation) -> None: def get_current_content(self) -> str: return self.doc def undo_last(self) -> None: def redo_last(self) -> None: Requirements: - apply_operation must support appending chars_to_insert to the end and deleting up to num_chars_to_delete characters from the end (no error if fewer characters exist). - get_current_content returns the current string; the document starts empty. - undo_last reverts the most recent applied operation; redo_last reapplies the most recent undone operation. - After any successful apply_operation, clear the redo history. - Ensure each operation runs in time proportional to the size of the change (avoid copying the entire document per step). Choose suitable data structures and an approach to store inverse operations. Discuss: data structures used (e.g., stacks/chunked buffer), how inverse operations are computed, time/space complexity of each method, and key edge cases (e.g., deleting more than available, multiple undos/redos).

This question evaluates implementation-level skills in state management, reversible operation design, and efficient mutable-string handling within the Coding & Algorithms domain.

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This is a Medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Notion.

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Implement text editor with undo/redo | Notion Interview Question

Implement a text document with undo/redo based on this Python skeleton:

class Operation:

class InsertAtEndOperation(Operation): def init(self, chars_to_insert: str): self.chars_to_insert = chars_to_insert

class DeleteFromEndOperation(Operation): def init(self, num_chars_to_delete: int): self.num_chars_to_delete = num_chars_to_delete

class TextDocument: def init(self) -> None:

def apply_operation(self, op: Operation) -> None:

def get_current_content(self) -> str:
    return self.doc

def undo_last(self) -> None:

def redo_last(self) -> None:

Requirements:

apply_operation must support appending chars_to_insert to the end and deleting up to num_chars_to_delete characters from the end (no error if fewer characters exist).
get_current_content returns the current string; the document starts empty.
undo_last reverts the most recent applied operation; redo_last reapplies the most recent undone operation.
After any successful apply_operation, clear the redo history.
Ensure each operation runs in time proportional to the size of the change (avoid copying the entire document per step). Choose suitable data structures and an approach to store inverse operations. Discuss: data structures used (e.g., stacks/chunked buffer), how inverse operations are computed, time/space complexity of each method, and key edge cases (e.g., deleting more than available, multiple undos/redos).