---
title: "LeetCode #705: Design HashSet"
url: https://perrotta.dev/2026/01/leetcode-%23705-design-hashset/
last_updated: 2026-01-06
---


[LeetCode #705: Design HashSet](https://leetcode.com/problems/design-hashset):

Shortcut:

```python
class MyHashSet:

    def __init__(self):
        self.s = set()

    def add(self, key: int) -> None:
        self.s.add(key)

    def remove(self, key: int) -> None:
        if key in self.s:
            self.s.remove(key)

    def contains(self, key: int) -> bool:
        return key in self.s


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

Proper:

```python
class MyHashSet:

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

    def hash(self, key):
        assert isinstance(key, int)
        return key % self.size

    def add(self, key: int) -> None:
        bucket = self.s[self.hash(key)]
        if key not in bucket:
            bucket.append(key)

    def remove(self, key: int) -> None:
        bucket = self.s[self.hash(key)]
        if key in bucket:
            del bucket[bucket.index(key)]

    def contains(self, key: int) -> bool:
        bucket = self.s[self.hash(key)]
        return key in bucket


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