Leetcode #2069: Walking Robot Simulation II
In this guide, we solve Leetcode #2069 Walking Robot Simulation II in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
A width x height grid is on an XY-plane with the bottom-left cell at (0, 0) and the top-right cell at (width - 1, height - 1). The grid is aligned with the four cardinal directions ("North", "East", "South", and "West").
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Design, Simulation
Intuition
We need to support multiple operations efficiently, so the internal design matters most.
Choosing the right combination of structures is the key to meeting the constraints.
Approach
List the required operations and select data structures that optimize them.
Implement each operation with clear invariants.
Steps:
- List the required operations.
- Pick supporting structures.
- Implement methods with clear invariants.
Example
Input
["Robot", "step", "step", "getPos", "getDir", "step", "step", "step", "getPos", "getDir"]
[[6, 3], [2], [2], [], [], [2], [1], [4], [], []]
Output
[null, null, null, [4, 0], "East", null, null, null, [1, 2], "West"]
Explanation
Robot robot = new Robot(6, 3); // Initialize the grid and the robot at (0, 0) facing East.
robot.step(2); // It moves two steps East to (2, 0), and faces East.
robot.step(2); // It moves two steps East to (4, 0), and faces East.
robot.getPos(); // return [4, 0]
robot.getDir(); // return "East"
robot.step(2); // It moves one step East to (5, 0), and faces East.
// Moving the next step East would be out of bounds, so it turns and faces North.
// Then, it moves one step North to (5, 1), and faces North.
robot.step(1); // It moves one step North to (5, 2), and faces North (not West).
robot.step(4); // Moving the next step North would be out of bounds, so it turns and faces West.
// Then, it moves four steps West to (1, 2), and faces West.
robot.getPos(); // return [1, 2]
robot.getDir(); // return "West"
Python Solution
Complexity
The time complexity is Varies by operation. The space complexity is Varies by operation.
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.