HashSet<Integer> set; // 位置

Deque<Integer> deque;

int score;

int foodIndex;

int width;

int height;

int[][] food;

public DesignSnakeGame(int width, int height, int[][] food) {

this.width = width;

this.height = height;

this.food = food;

set = new HashSet<>();

deque = new LinkedList<>();

score = 0;

foodIndex = 0;

set.add(0);

deque.offerLast(0);

}

public int move(String direction) {

if (score == -1) {

return -1;

}

int rowHead = deque.peekFirst() / width;

int colHead = deque.peekFirst() % width;

switch (direction) {

case "U" : rowHead--;

break;

case "D" : rowHead++;

break;

case "L" : colHead--;

break;

default : colHead++;

}

int head = rowHead * width + colHead;

set.remove(deque.peekLast());

if (rowHead < 0 || rowHead == height || colHead < 0 || colHead == width || set.contains(head)) {

return score = -1;

}

set.add(head);

deque.offerFirst(head);

if (foodIndex < food.length && rowHead == food[foodIndex][0] && colHead == food[foodIndex][1]) {

foodIndex++;

++score;

set.add(deque.peekLast());

return score;

}

deque.pollLast();

return score;

}