Problem URL: Design hashset

We will use a boolean array to store the values. We will use the value as the index of the array and set the value to true if the value is added and false if the value is removed.

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

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

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

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

Time complexity: O(1)
Space complexity: O(n), n is the number of values

We can use hashset to store the values. Then we can use the add, remove and contains methods of the hashset.

class MyHashSet:
    def __init__(self):
        self.hashset = set()

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

    def remove(self, key: int) -> None:
        self.hashset.discard(key)

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

Time complexity: O(1)
Space complexity: O(n), n is the number of values