0706-design-hashmap.rb

# frozen_string_literal: true

# 706. Design HashMap
# Easy
# https://leetcode.com/problems/design-hashmap

=begin
Design a HashMap without using any built-in hash table libraries.
Implement the MyHashMap class:
* MyHashMap() initializes the object with an empty map.
* void put(int key, int value) inserts a (key, value) pair into the HashMap. If the key already exists in the map, update the corresponding value.
* int get(int key) returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
* void remove(key) removes the key and its corresponding value if the map contains the mapping for the key.

Example 1:
Input
["MyHashMap", "put", "put", "get", "get", "put", "get", "remove", "get"]
[[], [1, 1], [2, 2], [1], [3], [2, 1], [2], [2], [2]]
Output
[null, null, null, 1, -1, null, 1, null, -1]
Explanation
MyHashMap myHashMap = new MyHashMap();
myHashMap.put(1, 1); // The map is now [[1,1]]
myHashMap.put(2, 2); // The map is now [[1,1], [2,2]]
myHashMap.get(1);    // return 1, The map is now [[1,1], [2,2]]
myHashMap.get(3);    // return -1 (i.e., not found), The map is now [[1,1], [2,2]]
myHashMap.put(2, 1); // The map is now [[1,1], [2,1]] (i.e., update the existing value)
myHashMap.get(2);    // return 1, The map is now [[1,1], [2,1]]
myHashMap.remove(2); // remove the mapping for 2, The map is now [[1,1]]
myHashMap.get(2);    // return -1 (i.e., not found), The map is now [[1,1]]

Constraints:
0 <= key, value <= 106
At most 104 calls will be made to put, get, and remove.
=end

class MyHashMap
  def initialize
  end

  def put(key, value)
    instance_variable_set(trans_key(key), value)
  end

  def get(key)
    instance_variable_get(trans_key(key)) || -1
  end

  def remove(key)
    instance_variable_set(trans_key(key), nil)
  end

  private
    def trans_key(key)
      "@_#{key}"
    end
end

# Your MyHashMap object will be instantiated and called as such:
# obj = MyHashMap.new()
# obj.put(key, value)
# param_2 = obj.get(key)
# obj.remove(key)