模拟行走机器人

/*
 * Solution for the robot walking problem using Java Stream.
 * The robot starts at the origin (0, 0) facing north. It can receive commands to
 * turn left, turn right, or move forward. The robot must avoid obstacles and
 * find the maximum squared Euclidean distance from the origin.
 *
 * Approach:
 * 1. Define the directions for north, east, south, and west.
 * 2. Use a set to store obstacles for quick lookup.
 * 3. Use Java Stream API to process the commands and update the robot's state.
 */

import java.util.HashSet;
import java.util.Set;
import java.util.stream.IntStream;

public class RobotSimulatorStream {
    public int robotSim(int[] commands, int[][] obstacles) {
        int[][] directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
        Set<String> obstacleSet = new HashSet<>();
        for (int[] obstacle : obstacles) {
            obstacleSet.add(obstacle[0] + "," + obstacle[1]);
        }

        int[] position = {0, 0};
        int[] dir = {0};
        int[] maxDistSq = {0};

        IntStream.of(commands).forEach(command -> {
            if (command == -1) {
                dir[0] = (dir[0] + 1) % 4;
            } else if (command == -2) {
                dir[0] = (dir[0] + 3) % 4;
            } else {
                IntStream.range(0, command).forEach(i -> {
                    int newX = position[0] + directions[dir[0]][0];
                    int newY = position[1] + directions[dir[0]][1];
                    if (obstacleSet.contains(newX + "," + newY)) {
                        return;
                    }
                    position[0] = newX;
                    position[1] = newY;
                    maxDistSq[0] = Math.max(maxDistSq[0], position[0] * position[0] + position[1] * position[1]);
                });
            }
        });
        return maxDistSq[0];
    }
}