## DEV Community

Abhishek Chaudhary

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# Design HashSet

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:

Input
[[], [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(2); // set = [1, 2]
myHashSet.contains(1); // return True
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 `104` calls will be made to `add`, `remove`, and `contains`.

SOLUTION:

``````import bisect

class MyHashSet:

def __init__(self):
self.size = 107
self.arr = [[] for i in range(self.size)]

def hfn(self, key):
key = ((key >> 16) ^ key) * 0x45d9f3b
key = ((key >> 16) ^ key) * 0x45d9f3b
key = (key >> 16) ^ key
return key % self.size

def add(self, key: int) -> None:
pos = bisect.bisect_left(self.arr[self.hfn(key)], key)
if pos >= len(self.arr[self.hfn(key)]) or self.arr[self.hfn(key)][pos] != key:
self.arr[self.hfn(key)].insert(pos, key)

def remove(self, key: int) -> None:
pos = bisect.bisect_left(self.arr[self.hfn(key)], key)
if pos < len(self.arr[self.hfn(key)]) and self.arr[self.hfn(key)][pos] == key:
del self.arr[self.hfn(key)][pos]

def contains(self, key: int) -> bool:
pos = bisect.bisect_left(self.arr[self.hfn(key)], key)
if pos < len(self.arr[self.hfn(key)]) and self.arr[self.hfn(key)][pos] == key:
return True
return False

# Your MyHashSet object will be instantiated and called as such:
# obj = MyHashSet()