How should I practice Text Editor, Part 2: Undo and Redo?

Start by reading the full statement, solve the visible examples, then compare the pattern against related OpenAI phone screen problems in FastPrep.

Is Text Editor, Part 2: Undo and Redo associated with OpenAI?

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Problem · Design

Text Editor, Part 2: Undo and Redo

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OpenAIFULLTIMEPHONE SCREEN

Problem statement

Extend a text buffer with undo and redo history. The buffer begins empty.

Supported operations

Each operation is a string array:

["INSERT", position, text]: insert text immediately before the character at the zero-based position.
["DELETE", start, end]: delete the characters in the half-open range [start, end).
["UNDO"]: undo the most recent insert or delete that is still applied.
["REDO"]: reapply the most recently undone operation.
["GET"]: append the complete current text to the output.

Every insert and delete must be undoable. Executing a new insert or delete after an undo clears the redo history. UNDO or REDO does nothing when its corresponding history is empty.

Interview sequence

Function

processTextEditorHistory(operations: String[][]) → String[]

Examples

Example 1

operations = [["INSERT", "0", "hello"], ["INSERT", "5", "!"], ["DELETE", "1", "4"], ["GET"], ["UNDO"], ["GET"], ["REDO"], ["GET"], ["UNDO"], ["INSERT", "5", "?"], ["REDO"], ["GET"]]return = ["ho!", "hello!", "ho!", "hello?!"]

Undo restores the deleted substring and redo removes it again. After the second undo, inserting ? clears the redo history, so the following REDO has no effect.