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Problem

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]ExplanationMyHashSet myHashSet = new MyHashSet();myHashSet.add(1);      // set = [1]myHashSet.add(2);      // set = [1, 2]myHashSet.contains(1); // return TruemyHashSet.contains(3); // return False, (not found)myHashSet.add(2);      // set = [1, 2]myHashSet.contains(2); // return TruemyHashSet.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.

Sol

class MyHashSet:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.hash = set()
        

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

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

    def contains(self, key: int) -> bool:
        """
        Returns true if this set contains the specified element
        """
        return key in self.hash