# 705. Design HashSet

#### Easy

***

Design a HashSet without using any built-in hash table libraries.

Implement `MyHashSet` class:

* `void add(key)` Inserts the value `key` into the HashSet.
* `bool contains(key)` Returns whether the value `key` exists in the HashSet or not.
* `void remove(key)` Removes the value `key` in the HashSet. If `key` does not exist in the HashSet, do nothing.

 

**Example 1:**

```java
Input
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
Output
[null, null, null, true, false, null, true, null, false]

Explanation
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1);      // set = [1]
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(1); // return True
myHashSet.contains(3); // return False, (not found)
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(2); // return True
myHashSet.remove(2);   // set = [1]
myHashSet.contains(2); // return False, (already removed)
```

 

**Constraints:**

* `0 <= key <= 106`
* At most `10^4` calls will be made to `add`, `remove`, and `contains`.

```python
class MyHashSet:

    def __init__(self):
        self.size = 10**4
        self.arr = [None]*(self.size)
        
    def hash(self, key):
        return key  % self.size

    def add(self, key: int) -> None:
        h = self.hash(key)
        if self.arr[h] is None:
            self.arr[h] = [key]
        else:
            self.arr[h].append(key)

    def remove(self, key: int) -> None:
        h = self.hash(key)
        if self.arr[h] is not None:
            while key in self.arr[h]:
                self.arr[h].remove(key)

    def contains(self, key: int) -> bool:
        h = self.hash(key)
        if self.arr[h] is not None:
            return key in self.arr[h]
```