Question

353. Design Snake Game

中文文档

Description

Design a Snake game that is played on a device with screen size height x width. Play the game online if you are not familiar with the game.

The snake is initially positioned at the top left corner (0, 0) with a length of 1 unit.

You are given an array food where food[i] = (ri, ci) is the row and column position of a piece of food that the snake can eat. When a snake eats a piece of food, its length and the game's score both increase by 1.

Each piece of food appears one by one on the screen, meaning the second piece of food will not appear until the snake eats the first piece of food.

When a piece of food appears on the screen, it is guaranteed that it will not appear on a block occupied by the snake.

The game is over if the snake goes out of bounds (hits a wall) or if its head occupies a space that its body occupies after moving (i.e. a snake of length 4 cannot run into itself).

Implement the SnakeGame class:

• SnakeGame(int width, int height, int[][] food) Initializes the object with a screen of size height x width and the positions of the food.
• int move(String direction) Returns the score of the game after applying one direction move by the snake. If the game is over, return -1.

 

Example 1:

Input
["SnakeGame", "move", "move", "move", "move", "move", "move"]
[[3, 2, [[1, 2], [0, 1]]], ["R"], ["D"], ["R"], ["U"], ["L"], ["U"]]
Output
[null, 0, 0, 1, 1, 2, -1]

Explanation
SnakeGame snakeGame = new SnakeGame(3, 2, [[1, 2], [0, 1]]);
snakeGame.move("R"); // return 0
snakeGame.move("D"); // return 0
snakeGame.move("R"); // return 1, snake eats the first piece of food. The second piece of food appears at (0, 1).
snakeGame.move("U"); // return 1
snakeGame.move("L"); // return 2, snake eats the second food. No more food appears.
snakeGame.move("U"); // return -1, game over because snake collides with border

 

Constraints:

• 1 <= width, height <= 104
• 1 <= food.length <= 50
• food[i].length == 2
• 0 <= ri < height
• 0 <= ci < width
• direction.length == 1
• direction is 'U', 'D', 'L', or 'R'.
• At most 104 calls will be made to move.

Solutions

Solution 1

class SnakeGame:
  def __init__(self, width: int, height: int, food: List[List[int]]):
    self.m = height
    self.n = width
    self.food = food
    self.score = 0
    self.idx = 0
    self.q = deque([(0, 0)])
    self.vis = {(0, 0)}

  def move(self, direction: str) -> int:
    i, j = self.q[0]
    x, y = i, j
    match direction:
      case "U":
        x -= 1
      case "D":
        x += 1
      case "L":
        y -= 1
      case "R":
        y += 1
    if x < 0 or x >= self.m or y < 0 or y >= self.n:
      return -1
    if (
      self.idx < len(self.food)
      and x == self.food[self.idx][0]
      and y == self.food[self.idx][1]
    ):
      self.score += 1
      self.idx += 1
    else:
      self.vis.remove(self.q.pop())
    if (x, y) in self.vis:
      return -1
    self.q.appendleft((x, y))
    self.vis.add((x, y))
    return self.score


# Your SnakeGame object will be instantiated and called as such:
# obj = SnakeGame(width, height, food)
# param_1 = obj.move(direction)

class SnakeGame {
  private int m;
  private int n;
  private int[][] food;
  private int score;
  private int idx;
  private Deque<Integer> q = new ArrayDeque<>();
  private Set<Integer> vis = new HashSet<>();

  public SnakeGame(int width, int height, int[][] food) {
    m = height;
    n = width;
    this.food = food;
    q.offer(0);
    vis.add(0);
  }

  public int move(String direction) {
    int p = q.peekFirst();
    int i = p / n, j = p % n;
    int x = i, y = j;
    if ("U".equals(direction)) {
      --x;
    } else if ("D".equals(direction)) {
      ++x;
    } else if ("L".equals(direction)) {
      --y;
    } else {
      ++y;
    }
    if (x < 0 || x >= m || y < 0 || y >= n) {
      return -1;
    }
    if (idx < food.length && x == food[idx][0] && y == food[idx][1]) {
      ++score;
      ++idx;
    } else {
      int t = q.pollLast();
      vis.remove(t);
    }
    int cur = f(x, y);
    if (vis.contains(cur)) {
      return -1;
    }
    q.offerFirst(cur);
    vis.add(cur);
    return score;
  }

  private int f(int i, int j) {
    return i * n + j;
  }
}

/**
 * Your SnakeGame object will be instantiated and called as such:
 * SnakeGame obj = new SnakeGame(width, height, food);
 * int param_1 = obj.move(direction);
 */

class SnakeGame {
public:
  SnakeGame(int width, int height, vector<vector<int>>& food) {
    m = height;
    n = width;
    this->food = food;
    score = 0;
    idx = 0;
    q.push_back(0);
    vis.insert(0);
  }

  int move(string direction) {
    int p = q.front();
    int i = p / n, j = p % n;
    int x = i, y = j;
    if (direction == "U") {
      --x;
    } else if (direction == "D") {
      ++x;
    } else if (direction == "L") {
      --y;
    } else {
      ++y;
    }
    if (x < 0 || x >= m || y < 0 || y >= n) {
      return -1;
    }
    if (idx < food.size() && x == food[idx][0] && y == food[idx][1]) {
      ++score;
      ++idx;
    } else {
      int tail = q.back();
      q.pop_back();
      vis.erase(tail);
    }
    int cur = f(x, y);
    if (vis.count(cur)) {
      return -1;
    }
    q.push_front(cur);
    vis.insert(cur);
    return score;
  }

private:
  int m;
  int n;
  vector<vector<int>> food;
  int score;
  int idx;
  deque<int> q;
  unordered_set<int> vis;

  int f(int i, int j) {
    return i * n + j;
  }
};

/**
 * Your SnakeGame object will be instantiated and called as such:
 * SnakeGame* obj = new SnakeGame(width, height, food);
 * int param_1 = obj->move(direction);
 */

type SnakeGame struct {
  m   int
  n   int
  food  [][]int
  score int
  idx   int
  q   []int
  vis   map[int]bool
}

func Constructor(width int, height int, food [][]int) SnakeGame {
  return SnakeGame{height, width, food, 0, 0, []int{0}, map[int]bool{}}
}

func (this *SnakeGame) Move(direction string) int {
  f := func(i, j int) int {
    return i*this.n + j
  }
  p := this.q[0]
  i, j := p/this.n, p%this.n
  x, y := i, j
  if direction == "U" {
    x--
  } else if direction == "D" {
    x++
  } else if direction == "L" {
    y--
  } else {
    y++
  }
  if x < 0 || x >= this.m || y < 0 || y >= this.n {
    return -1
  }
  if this.idx < len(this.food) && x == this.food[this.idx][0] && y == this.food[this.idx][1] {
    this.score++
    this.idx++
  } else {
    t := this.q[len(this.q)-1]
    this.q = this.q[:len(this.q)-1]
    this.vis[t] = false
  }
  cur := f(x, y)
  if this.vis[cur] {
    return -1
  }
  this.q = append([]int{cur}, this.q...)
  this.vis[cur] = true
  return this.score
}

/**
 * Your SnakeGame object will be instantiated and called as such:
 * obj := Constructor(width, height, food);
 * param_1 := obj.Move(direction);
 */

class SnakeGame {
  private m: number;
  private n: number;
  private food: number[][];
  private score: number;
  private idx: number;
  private q: number[];
  private vis: Set<number>;

  constructor(width: number, height: number, food: number[][]) {
    this.m = height;
    this.n = width;
    this.food = food;
    this.score = 0;
    this.idx = 0;
    this.q = [0];
    this.vis = new Set([0]);
  }

  move(direction: string): number {
    const p = this.q[0];
    const i = Math.floor(p / this.n);
    const j = p % this.n;
    let x = i;
    let y = j;
    if (direction === 'U') {
      --x;
    } else if (direction === 'D') {
      ++x;
    } else if (direction === 'L') {
      --y;
    } else {
      ++y;
    }
    if (x < 0 || x >= this.m || y < 0 || y >= this.n) {
      return -1;
    }
    if (
      this.idx < this.food.length &&
      x === this.food[this.idx][0] &&
      y === this.food[this.idx][1]
    ) {
      ++this.score;
      ++this.idx;
    } else {
      const t = this.q.pop()!;
      this.vis.delete(t);
    }
    const cur = x * this.n + y;
    if (this.vis.has(cur)) {
      return -1;
    }
    this.q.unshift(cur);
    this.vis.add(cur);
    return this.score;
  }
}

/**
 * Your SnakeGame object will be instantiated and called as such:
 * var obj = new SnakeGame(width, height, food)
 * var param_1 = obj.move(direction)
 */