Batch Commit and Batch Undo | Dataford Interview Questions

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Problem

Figma groups several related FigJam or Figma Design canvas edits into one history entry so a single undo removes the entire user action. Implement batch_commit and batch_undo for a simplified document model.

A document is a dictionary mapping object IDs to integer values. Each change is represented as [object_id, before, after]. A batch commit must apply every change and store the entire batch as one undo entry. A batch undo must restore the most recent batch in reverse order. If there is no committed batch, undo does nothing.

Implement process_operations, which uses these operations:

{"type": "commit", "changes": [[id, before, after], ...]}
{"type": "undo"}

Return the final document dictionary. The input document should not be mutated by the caller.

Formal Specification

Input: initial_document, a dictionary from strings to integers, and actions, a list of commit or undo dictionaries.

Output: A dictionary containing the document state after all actions.

Constraints

0 <= len(actions) <= 10^5
Each action contains at most 10^4 changes
Each object appears at most once within a committed batch
Every before value matches the current document value
Object IDs are nonempty strings and values are integers

Function Signature

def process_operations(initial_document, actions):