Question

705. 设计哈希集合

English Version

题目描述

不使用任何内建的哈希表库设计一个哈希集合（HashSet）。

实现 MyHashSet 类：

• void add(key) 向哈希集合中插入值 key 。
• bool contains(key) 返回哈希集合中是否存在这个值 key 。
• void remove(key) 将给定值 key 从哈希集合中删除。如果哈希集合中没有这个值，什么也不做。

 

示例：

输入：
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
输出：
[null, null, null, true, false, null, true, null, false]

解释：
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1);    // set = [1]
myHashSet.add(2);    // set = [1, 2]
myHashSet.contains(1); // 返回 True
myHashSet.contains(3); // 返回 False ，（未找到）
myHashSet.add(2);    // set = [1, 2]
myHashSet.contains(2); // 返回 True
myHashSet.remove(2);   // set = [1]
myHashSet.contains(2); // 返回 False ，（已移除）

 

提示：

• 0 <= key <= 106
• 最多调用 104 次 add、remove 和 contains

解法

方法一：静态数组实现

直接创建一个大小为 $1000001$ 的数组，初始时数组中的每个元素都为 false，表示哈希集合中不存在该元素。

往哈希集合添加元素时，将数组中对应位置的值置为 true；删除元素时，将数组中对应位置的值置为 false；当查询元素是否存在时，直接返回数组中对应位置的值即可。

以上操作的时间复杂度均为 $O(1)$。

class MyHashSet:
  def __init__(self):
    self.data = [False] * 1000001

  def add(self, key: int) -> None:
    self.data[key] = True

  def remove(self, key: int) -> None:
    self.data[key] = False

  def contains(self, key: int) -> bool:
    return self.data[key]


# Your MyHashSet object will be instantiated and called as such:
# obj = MyHashSet()
# obj.add(key)
# obj.remove(key)
# param_3 = obj.contains(key)

class MyHashSet {
  private boolean[] data = new boolean[1000001];

  public MyHashSet() {
  }

  public void add(int key) {
    data[key] = true;
  }

  public void remove(int key) {
    data[key] = false;
  }

  public boolean contains(int key) {
    return data[key];
  }
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet obj = new MyHashSet();
 * obj.add(key);
 * obj.remove(key);
 * boolean param_3 = obj.contains(key);
 */

class MyHashSet {
public:
  bool data[1000001];

  MyHashSet() {
    memset(data, false, sizeof data);
  }

  void add(int key) {
    data[key] = true;
  }

  void remove(int key) {
    data[key] = false;
  }

  bool contains(int key) {
    return data[key];
  }
};

/**
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet* obj = new MyHashSet();
 * obj->add(key);
 * obj->remove(key);
 * bool param_3 = obj->contains(key);
 */

type MyHashSet struct {
  data []bool
}

func Constructor() MyHashSet {
  data := make([]bool, 1000010)
  return MyHashSet{data}
}

func (this *MyHashSet) Add(key int) {
  this.data[key] = true
}

func (this *MyHashSet) Remove(key int) {
  this.data[key] = false
}

func (this *MyHashSet) Contains(key int) bool {
  return this.data[key]
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Add(key);
 * obj.Remove(key);
 * param_3 := obj.Contains(key);
 */

class MyHashSet {
  data: Array<boolean>;
  constructor() {
    this.data = new Array(10 ** 6 + 1).fill(false);
  }

  add(key: number): void {
    this.data[key] = true;
  }

  remove(key: number): void {
    this.data[key] = false;
  }

  contains(key: number): boolean {
    return this.data[key];
  }
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * var obj = new MyHashSet()
 * obj.add(key)
 * obj.remove(key)
 * var param_3 = obj.contains(key)
 */

方法二：数组嵌套链表

我们也可以开辟一个大小为 SIZE=1000 的数组，数组的每个位置是一个链表。

class MyHashSet:
  def __init__(self):
    self.size = 1000
    self.data = [[] for _ in range(self.size)]

  def add(self, key: int) -> None:
    if self.contains(key):
      return
    idx = self.hash(key)
    self.data[idx].append(key)

  def remove(self, key: int) -> None:
    if not self.contains(key):
      return
    idx = self.hash(key)
    self.data[idx].remove(key)

  def contains(self, key: int) -> bool:
    idx = self.hash(key)
    return any(v == key for v in self.data[idx])

  def hash(self, key) -> int:
    return key % self.size


# Your MyHashSet object will be instantiated and called as such:
# obj = MyHashSet()
# obj.add(key)
# obj.remove(key)
# param_3 = obj.contains(key)

class MyHashSet {
  private static final int SIZE = 1000;
  private LinkedList[] data;

  public MyHashSet() {
    data = new LinkedList[SIZE];
    for (int i = 0; i < SIZE; ++i) {
      data[i] = new LinkedList<Integer>();
    }
  }

  public void add(int key) {
    if (contains(key)) {
      return;
    }
    int idx = hash(key);
    data[idx].addFirst(key);
  }

  public void remove(int key) {
    if (!contains(key)) {
      return;
    }
    int idx = hash(key);
    data[idx].remove(Integer.valueOf(key));
  }

  public boolean contains(int key) {
    int idx = hash(key);
    Iterator<Integer> it = data[idx].iterator();
    while (it.hasNext()) {
      Integer e = it.next();
      if (e == key) {
        return true;
      }
    }
    return false;
  }

  private int hash(int key) {
    return key % SIZE;
  }
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet obj = new MyHashSet();
 * obj.add(key);
 * obj.remove(key);
 * boolean param_3 = obj.contains(key);
 */

class MyHashSet {
private:
  int size = 1000;
  vector<list<int>> data;

public:
  MyHashSet()
    : data(size) {
  }

  void add(int key) {
    if (contains(key)) {
      return;
    }
    int idx = hash(key);
    data[idx].push_back(key);
  }

  void remove(int key) {
    if (!contains(key)) {
      return;
    }
    int idx = hash(key);
    data[idx].remove(key);
  }

  bool contains(int key) {
    int idx = hash(key);
    for (auto it = data[idx].begin(); it != data[idx].end(); it++) {
      if ((*it) == key) {
        return true;
      }
    }
    return false;
  }

  int hash(int key) {
    return key % size;
  }
};

/**
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet* obj = new MyHashSet();
 * obj->add(key);
 * obj->remove(key);
 * bool param_3 = obj->contains(key);
 */

type MyHashSet struct {
  data []list.List
}

func Constructor() MyHashSet {
  return MyHashSet{make([]list.List, 1000)}
}

func (this *MyHashSet) Add(key int) {
  if this.Contains(key) {
    return
  }
  idx := this.hash(key)
  this.data[idx].PushBack(key)
}

func (this *MyHashSet) Remove(key int) {
  idx := this.hash(key)
  for e := this.data[idx].Front(); e != nil; e = e.Next() {
    if e.Value.(int) == key {
      this.data[idx].Remove(e)
    }
  }
}

func (this *MyHashSet) Contains(key int) bool {
  idx := this.hash(key)
  for e := this.data[idx].Front(); e != nil; e = e.Next() {
    if e.Value.(int) == key {
      return true
    }
  }
  return false
}

func (this *MyHashSet) hash(key int) int {
  return key % len(this.data)
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Add(key);
 * obj.Remove(key);
 * param_3 := obj.Contains(key);
 */