贪吃蛇

/*
 * Problem: LeetCode 353 - Design Snake Game
 * 
 * The implementation using Java Streams focuses more on functional-style operations.
 * We use streams where possible, although this problem is inherently stateful and stream usage is limited.
 */
 
import java.util.*;
import java.util.stream.Collectors;
 
public class SnakeGameStream {
    private int width, height, score;
    private Deque<int[]> snake;
    private Set<String> snakeSet;
    private List<int[]> food;
    private int foodIndex;
 
    public SnakeGameStream(int width, int height, int[][] food) {
        this.width = width;
        this.height = height;
        this.food = Arrays.stream(food).collect(Collectors.toList());
        this.score = 0;
        this.foodIndex = 0;
        this.snake = new LinkedList<>();
        this.snakeSet = new HashSet<>();
        this.snake.add(new int[]{0, 0});
        this.snakeSet.add("0_0");
    }
 
    public int move(String direction) {
        int[] head = snake.peekFirst();
        int x = head[0], y = head[1];
        switch (direction) {
            case "U": x--; break;
            case "L": y--; break;
            case "R": y++; break;
            case "D": x++; break;
        }
 
        String newHeadPos = x + "_" + y;
        if (x < 0 || x >= height || y < 0 || y >= width || (snakeSet.contains(newHeadPos) && !newHeadPos.equals(snake.peekLast()[0] + "_" + snake.peekLast()[1]))) {
            return -1;
        }
 
        snake.addFirst(new int[]{x, y});
        snakeSet.add(newHeadPos);
 
        if (foodIndex < food.size() && Arrays.equals(food.get(foodIndex), new int[]{x, y})) {
            score++;
            foodIndex++;
        } else {
            int[] tail = snake.removeLast();
            snakeSet.remove(tail[0] + "_" + tail[1]);
        }
 
        return score;
    }
}