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:

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.

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]

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