Python 3 | 144 ms | Faster than 99.40%
\tdef init(self):\n\t\t\t"""\n\t\t\tInitialize your data structure here.\n\t\t\t"""\n\t\t\tself.arr = bytearray(1000001)\n\n\n    def add(self, key: int) -> Non
\tdef __init__(self):\n\t\t\t"""\n\t\t\tInitialize your data structure here.\n\t\t\t"""\n\t\t\tself.arr = bytearray(1000001)\n\n\n    def add(self, key: int) -> None:\n        if not self.arr[key]:\n            self.arr[key] = True\n        \n\n\tdef remove(self, key: int) -> None:\n        if self.arr[key]:\n            self.arr[key]=False\n\n    def contains(self, key: int) -> bool:\n        """\n        Returns true if this set contains the specified element\n        """\n        if self.arr[key]:\n            return True\n        else:\n            return False\n\t\t\t\nDrop a like/upvote if you find this useful!
['Python3']