OpenSheet: Spreadsheet with Cell Dependencies

Problem Overview

Design and implement a spreadsheet system called OpenSheet that supports cell values, formulas, and automatic dependency resolution. The system must handle cell references, evaluate formulas, and detect circular dependencies. This problem tests your ability to build a dependency graph, perform topological evaluation, and optimize for different performance requirements.

Part 1: Basic Implementation with Real-Time Evaluation

Implement a Spreadsheet class that supports setting values/formulas and getting computed values with real-time dependency resolution.

Requirements

• Constructor: Spreadsheet() - Initializes the spreadsheet
• Set Cell: setCell(key: str, value: str) - Sets a cell to a value or formula
• Values can be numbers (e.g., "42", "3.14")
• Formulas start with = and can reference other cells (e.g., "=A1 + A2")
• Formulas support basic arithmetic: +, -, *, /
• Cell references use standard spreadsheet notation (e.g., A1, B2, Z99)
• Get Cell: getCell(key: str) -> float - Returns the computed value of a cell
• For value cells, returns the numeric value
• For formula cells, recursively evaluates dependencies and returns result
• Raises error for circular dependencies
• Returns 0 or None for non-existent cells (implementation choice)

Example Usage

`spreadsheet = Spreadsheet()

Set simple values

spreadsheet.setCell('A1', '1') spreadsheet.setCell('A2', '2')

Set formulas with dependencies

spreadsheet.setCell('A3', '=A1 + A2') # A3 = 1 + 2 = 3 spreadsheet.setCell($L41, $L42) $L43 spreadsheet.setCell($L44, $L45) $L46 $L48(spreadsheet.getCell($L49)) $L4a $L4b(spreadsheet.getCell($L4c)) $L4d $L4e(spreadsheet.getCell($L4f)) $L50 spreadsheet.setCell($L52, $L53) $L54(spreadsheet.getCell($L55)) $L56 $L57(spreadsheet.getCell($L58)) $L59 $L5b(spreadsheet.getCell($L5c)) $L5d