机器人大冒险

/*
 * Problem: A robot starts at (0, 0) and can follow a repeating command sequence to move on a 2D plane.
 * The command sequence consists of 'U' (up) and 'R' (right) moves. 
 * There are obstacles on the plane that the robot must avoid.
 * Given the target coordinates (x, y), determine if the robot can reach the target without hitting any obstacles.
 */

import java.util.Arrays;

public class RobotPathStream {
    public boolean canReach(String command, int[][] obstacles, int x, int y) {
        // Calculate the end position after one full cycle of the command
        int cycleX = 0, cycleY = 0;
        for (char c : command.toCharArray()) {
            if (c == 'U') cycleY++;
            else if (c == 'R') cycleX++;
        }

        // Helper function to check if a position is reachable without hitting obstacles
        boolean isReachable(int tx, int ty) {
            if (tx < 0 || ty < 0) return false;
            int cycles = Math.min(tx / cycleX, ty / cycleY);
            int remainingX = tx - cycles * cycleX;
            int remainingY = ty - cycles * cycleY;

            return command.chars().anyMatch(c -> {
                if (c == 'U') remainingY--;
                else if (c == 'R') remainingX--;
                return remainingX == 0 && remainingY == 0;
            });
        }

        // Check if the target is reachable
        if (!isReachable(x, y)) return false;

        // Check if any obstacle is on the path
        return Arrays.stream(obstacles).noneMatch(obstacle -> isReachable(obstacle[0], obstacle[1]));
    }
}