706. Design HashMap

Problem

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.

Solution

var MyHashMap = function() {
    this.map = [];
};

/** 
 * @param {number} key 
 * @param {number} value
 * @return {void}
 */
MyHashMap.prototype.put = function(key, value) {
    this.map[key] = value;
};

/** 
 * @param {number} key
 * @return {number}
 */
MyHashMap.prototype.get = function(key) {
    return this.map[key] ?? -1;
};

/** 
 * @param {number} key
 * @return {void}
 */
MyHashMap.prototype.remove = function(key) {
    this.map[key] = undefined;
};

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

Explain:

nope.

Complexity:

• Time complexity : O(1).
• Space complexity : O(1).