Question

面试题 03.06. 动物收容所

English Version

题目描述

动物收容所。有家动物收容所只收容狗与猫，且严格遵守“先进先出”的原则。在收养该收容所的动物时，收养人只能收养所有动物中“最老”（由其进入收容所的时间长短而定）的动物，或者可以挑选猫或狗（同时必须收养此类动物中“最老”的）。换言之，收养人不能自由挑选想收养的对象。请创建适用于这个系统的数据结构，实现各种操作方法，比如enqueue、dequeueAny、dequeueDog和dequeueCat。允许使用Java内置的LinkedList数据结构。

enqueue方法有一个animal参数，animal[0]代表动物编号，animal[1]代表动物种类，其中 0 代表猫，1 代表狗。

dequeue*方法返回一个列表[动物编号, 动物种类]，若没有可以收养的动物，则返回[-1,-1]。

示例1:

 输入：
["AnimalShelf", "enqueue", "enqueue", "dequeueCat", "dequeueDog", "dequeueAny"]
[[], [[0, 0]], [[1, 0]], [], [], []]
 输出：
[null,null,null,[0,0],[-1,-1],[1,0]]

示例2:

 输入：
["AnimalShelf", "enqueue", "enqueue", "enqueue", "dequeueDog", "dequeueCat", "dequeueAny"]
[[], [[0, 0]], [[1, 0]], [[2, 1]], [], [], []]
 输出：
[null,null,null,null,[2,1],[0,0],[1,0]]

说明:

1. 收纳所的最大容量为20000

解法

方法一

class AnimalShelf:
  def __init__(self):
    self.cats = []
    self.dogs = []

  def enqueue(self, animal: List[int]) -> None:
    if animal[1] == 0:
      self.cats.insert(0, animal[0])
    else:
      self.dogs.insert(0, animal[0])

  def dequeueAny(self) -> List[int]:
    if len(self.dogs) == 0:
      return self.dequeueCat()
    if len(self.cats) == 0:
      return self.dequeueDog()
    return self.dequeueDog() if self.dogs[-1] < self.cats[-1] else self.dequeueCat()

  def dequeueDog(self) -> List[int]:
    return [-1, -1] if len(self.dogs) == 0 else [self.dogs.pop(), 1]

  def dequeueCat(self) -> List[int]:
    return [-1, -1] if len(self.cats) == 0 else [self.cats.pop(), 0]


# Your AnimalShelf object will be instantiated and called as such:
# obj = AnimalShelf()
# obj.enqueue(animal)
# param_2 = obj.dequeueAny()
# param_3 = obj.dequeueDog()
# param_4 = obj.dequeueCat()

class AnimalShelf {
  Queue<Integer> cats;
  Queue<Integer> dogs;
  public AnimalShelf() {
    cats = new LinkedList<>();
    dogs = new LinkedList<>();
  }

  public void enqueue(int[] animal) {
    if (animal[1] == 0) {
      cats.offer(animal[0]);
    } else {
      dogs.offer(animal[0]);
    }
  }

  public int[] dequeueAny() {
    return dogs.isEmpty()
      ? dequeueCat()
      : (cats.isEmpty() ? dequeueDog()
                : (dogs.peek() < cats.peek() ? dequeueDog() : dequeueCat()));
  }

  public int[] dequeueDog() {
    return dogs.isEmpty() ? new int[] {-1, -1} : new int[] {dogs.poll(), 1};
  }

  public int[] dequeueCat() {
    return cats.isEmpty() ? new int[] {-1, -1} : new int[] {cats.poll(), 0};
  }
}

/**
 * Your AnimalShelf object will be instantiated and called as such:
 * AnimalShelf obj = new AnimalShelf();
 * obj.enqueue(animal);
 * int[] param_2 = obj.dequeueAny();
 * int[] param_3 = obj.dequeueDog();
 * int[] param_4 = obj.dequeueCat();
 */

class AnimalShelf {
  private cats: number[];
  private dogs: number[];

  constructor() {
    this.cats = [];
    this.dogs = [];
  }

  enqueue(animal: number[]): void {
    const [i, j] = animal;
    this[j === 0 ? 'cats' : 'dogs'].push(i);
  }

  dequeueAny(): number[] {
    const n = this.dogs.length;
    const m = this.cats.length;
    if (n === 0 && m === 0) {
      return [-1, -1];
    }
    if ((this.dogs[0] ?? Infinity) < (this.cats[0] ?? Infinity)) {
      return [this.dogs.shift(), 1];
    } else {
      return [this.cats.shift(), 0];
    }
  }

  dequeueDog(): number[] {
    if (this.dogs.length === 0) {
      return [-1, -1];
    }
    return [this.dogs.shift(), 1];
  }

  dequeueCat(): number[] {
    if (this.cats.length === 0) {
      return [-1, -1];
    }
    return [this.cats.shift(), 0];
  }
}

/**
 * Your AnimalShelf object will be instantiated and called as such:
 * var obj = new AnimalShelf()
 * obj.enqueue(animal)
 * var param_2 = obj.dequeueAny()
 * var param_3 = obj.dequeueDog()
 * var param_4 = obj.dequeueCat()
 */

use std::collections::VecDeque;

struct AnimalShelf {
  cats: VecDeque<i32>,
  dogs: VecDeque<i32>,
}

/**
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
impl AnimalShelf {
  fn new() -> Self {
    Self {
      cats: VecDeque::new(),
      dogs: VecDeque::new(),
    }
  }

  fn enqueue(&mut self, animal: Vec<i32>) {
    if animal[1] == 0 {
      self.cats.push_back(animal[0]);
    } else {
      self.dogs.push_back(animal[0]);
    }
  }

  fn dequeue_any(&mut self) -> Vec<i32> {
    match (self.cats.is_empty(), self.dogs.is_empty()) {
      (true, true) => vec![-1, -1],
      (true, false) => self.dequeue_dog(),
      (false, true) => self.dequeue_cat(),
      (false, false) => {
        if self.dogs[0] < self.cats[0] { self.dequeue_dog() } else { self.dequeue_cat() }
      }
    }
  }

  fn dequeue_dog(&mut self) -> Vec<i32> {
    if self.dogs.is_empty() {
      return vec![-1, -1];
    }
    vec![self.dogs.pop_front().unwrap(), 1]
  }

  fn dequeue_cat(&mut self) -> Vec<i32> {
    if self.cats.is_empty() {
      return vec![-1, -1];
    }
    vec![self.cats.pop_front().unwrap(), 0]
  }
}/**
 * Your AnimalShelf object will be instantiated and called as such:
 * let obj = AnimalShelf::new();
 * obj.enqueue(animal);
 * let ret_2: Vec<i32> = obj.dequeue_any();
 * let ret_3: Vec<i32> = obj.dequeue_dog();
 * let ret_4: Vec<i32> = obj.dequeue_cat();
 */