706. Design HashMap

Problem

Tags: Array, Hash Table, Linked List, Design, Hash Function

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 <= 10^6
• At most 10^4 calls will be made to put, get, and remove.

Code

JS

// 706. Design HashMap (2/7/53841)
// Runtime: 192 ms (79.57%) Memory: 47.88 MB (94.93%) 


class MyHashMap {
    constructor() {
        this.size = 1e6;
        this.space = [];
    }
    
    put(key, val) {
        this.space[key % this.size] = val;
    }
    
    get(key) {
        return this.space[key % this.size] === undefined ? -1 : this.space[key % this.size];
    }
    
    remove(key) {
        delete this.space[key % this.size];
    }
}