Design a robot movement command system
Problem Description
Design and implement a small, testable module for controlling robot movement on a 2D grid. The system should be capable of representing a robot's state, receiving a sequence of commands, executing them to update the robot's position and direction, and crucially, be easily extensible to accommodate new command types over time.
Requirements
Robot State
- The robot's position is represented by
(x, y)coordinates on an integer grid. - The robot has a facing direction, which must be one of
N(North),E(East),S(South), orW(West).
Commands
Implement support for the following initial set of commands:
L: Rotate the robot 90 degrees left (e.g., North → West → South → East → North).R: Rotate the robot 90 degrees right (e.g., North → East → South → West → North).F: Move the robot forward by 1 step in its current facing direction.
Input/Output
- Input: The system will receive an initial robot state
(x0, y0, dir0)and a command string (e.g.,"FFLFFR") or an equivalent list/array of commands. - Output: The system must return the final robot state
(x, y, dir)after all commands have been executed.
Invalid Command Handling
- Define and implement a clear policy for handling unknown or invalid commands (e.g., throw an error, ignore the command, or collect errors). Clearly state your chosen policy.
Extensibility
- A core design requirement is that the set of valid commands will expand significantly over time (e.g.,
Bfor backward,Jfor jump,Ufor undo, etc.). - The design of the command system must ensure that adding a new command does not necessitate rewriting large portions of the existing robot execution logic.
- Discuss and/or implement a suitable command abstraction (e.g., using command objects, a registry/dispatcher pattern, or similar).
Testing
- Write small, incremental tests as you develop the module.
- Upon completion, be prepared to explain:
- What further optimizations you would consider.
- How you would approach systematic testing, including unit tests, property-based tests, and edge case handling.
Example
- Initial State:
(0, 0, N) - Commands:
"FFRFF" - Expected Final State:
(2, 2, E)
Constraints
- The command string length can be up to approximately 10^5 characters.
- The grid is unbounded; assume no walls or obstacles unless you explicitly choose to add boundary logic as an extension.
Deliverables
Implement the core classes/functions (e.g., Robot, command execution/dispatcher) and demonstrate their functionality with tests.
AI interview prep
Core dilemma
The central engineering conflict is balancing immediate functional correctness of robot movement with a highly extensible architecture that minimizes modification for future command additions. It's about designing for change.
3 tradeoffs and 3 stress tests locked
Interview prep
Unlock the interviewer X-Ray rubric, tradeoff matrix, stress tests, clarifying questions, and key concepts.
Design a robot movement command system
Problem Description
Design and implement a small, testable module for controlling robot movement on a 2D grid. The system should be capable of representing a robot's state, receiving a sequence of commands, executing them to update the robot's position and direction, and crucially, be easily extensible to accommodate new command types over time.
Requirements
Robot State
- The robot's position is represented by
(x, y)coordinates on an integer grid. - The robot has a facing direction, which must be one of
N(North),E(East),S(South), orW(West).
Commands
Implement support for the following initial set of commands:
L: Rotate the robot 90 degrees left (e.g., North → West → South → East → North).R: Rotate the robot 90 degrees right (e.g., North → East → South → West → North).F: Move the robot forward by 1 step in its current facing direction.
Input/Output
- Input: The system will receive an initial robot state
(x0, y0, dir0)and a command string (e.g.,"FFLFFR") or an equivalent list/array of commands. - Output: The system must return the final robot state
(x, y, dir)after all commands have been executed.
Invalid Command Handling
- Define and implement a clear policy for handling unknown or invalid commands (e.g., throw an error, ignore the command, or collect errors). Clearly state your chosen policy.
Extensibility
- A core design requirement is that the set of valid commands will expand significantly over time (e.g.,
Bfor backward,Jfor jump,Ufor undo, etc.). - The design of the command system must ensure that adding a new command does not necessitate rewriting large portions of the existing robot execution logic.
- Discuss and/or implement a suitable command abstraction (e.g., using command objects, a registry/dispatcher pattern, or similar).
Testing
- Write small, incremental tests as you develop the module.
- Upon completion, be prepared to explain:
- What further optimizations you would consider.
- How you would approach systematic testing, including unit tests, property-based tests, and edge case handling.
Example
- Initial State:
(0, 0, N) - Commands:
"FFRFF" - Expected Final State:
(2, 2, E)
Constraints
- The command string length can be up to approximately 10^5 characters.
- The grid is unbounded; assume no walls or obstacles unless you explicitly choose to add boundary logic as an extension.
Deliverables
Implement the core classes/functions (e.g., Robot, command execution/dispatcher) and demonstrate their functionality with tests.