0705-design-hashset.rb

# frozen_string_literal: true

# 705. Design HashSet
# https://leetcode.com/problems/design-hashset
# Easy

=begin
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 104 calls will be made to add, remove, and contains.
=end

class MyHashSet
  def initialize
    @array = Array.new(1000000)
  end


=begin
  :type key: Integer
  :rtype: Void
=end
  def add(key)
    @array[key] = true
  end


=begin
  :type key: Integer
  :rtype: Void
=end
  def remove(key)
    @array[key] = nil
  end


=begin
  :type key: Integer
  :rtype: Boolean
=end
  def contains(key)
    !!@array[key]
  end
end

# Your MyHashSet object will be instantiated and called as such:
# obj = MyHashSet.new()
# obj.add(key)
# obj.remove(key)
# param_3 = obj.contains(key)