874. Walking Robot Simulation

import java.util.HashSet;
import java.util.Set;

class Solution {
    public int robotSim(int[] commands, int[][] obstacles) {
        int x = 0, y = 0, d = 0;
        int[][] direction = { { 0, 1 }, { 1, 0 }, { 0, -1 }, { -1, 0 } };
        int maxDistance = 0;
        Set<String> obstacleSet = new HashSet<>();
        for (int[] obstacle : obstacles) {
            obstacleSet.add(obstacle[0] + "," + obstacle[1]);
        }
        for (int cmd : commands) {
            if (cmd == -1) {
                d = (d + 1) % 4;
            } else if (cmd == -2) {
                d = (d + 3) % 4;
            } else {
                for (int i = 0; i < cmd; i++) {
                    int nx = x + direction[d][0];
                    int ny = y + direction[d][1];
                    if (obstacleSet.contains(nx + "," + ny)) {
                        break;
                    }
                    x = nx;
                    y = ny;
                    maxDistance = Math.max(maxDistance, x * x + y * y);
                }
            }
        }
        return maxDistance;
    }
}