JavaScriptDesignHashSet.md

JavaScript Design HashSet

Challenge

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

Input: ['MyHashSet', 'add', 'add', 'contains', 'contains', 'add', 'contains', 'remove', 'contains']
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
Output: 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.

Solution

let MyHashSet = function() {};

MyHashSet.prototype.add = function(key) {
    this[key] = null;
};

MyHashSet.prototype.remove = function(key) {
    delete this[key];
};

MyHashSet.prototype.contains = function(key) {
    return this.hasOwnProperty(key);
};

Explanation

I've written a class called MyHashSet that represents a set of unique values. This class has three methods: add, remove, and contains.

The add method takes a key as a parameter and adds it as a property to the MyHashSet object. The value of the property is set to null.

The remove method takes a key as a parameter and deletes the property with that key from the MyHashSet object.

The contains method takes a key as a parameter and checks if the MyHashSet object has a property with that key. It returns true if the property exists, and false otherwise.

I used the prototype property of the MyHashSet class to define the methods. By doing so, all instances of the MyHashSet class will have access to these methods.

In the add method, the key is added as a property to the current instance of the MyHashSet object using the this keyword to refer to the current object.

In the remove method, the property with the specified key is deleted from the current instance of the MyHashSet object using the delete keyword.

In the contains method, the hasOwnProperty method is used to check if the current instance of the MyHashSet object has a property with the specified key. The method returns true if the property exists and false otherwise.

In summary, I've defined a class called MyHashSet with methods to add, remove, and check for the presence of a key in the set. This implementation allows for efficient management of a set of unique values.

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