Design a HashMap

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<sup>6</sup>

• At most 10<sup>4</sup> calls will be made to put, get, and remove.

Reference: https://leetcode.com/problems/design-hashmap/description/

Idea:

Implement with Golang:

type MyHashMap struct {
    Hm [][]*Node
} 

type Node struct {
    Key int
    Value int
}

func hash(key int) int {
    return key % 1000
}

func Constructor() MyHashMap {
    hm := make([][]*Node, 1000)
    return MyHashMap{
        Hm: hm,
    }
}


func (this *MyHashMap) Put(key int, value int)  {
    keyHash := hash(key)
    for index, element := range this.Hm[keyHash] {
        if element.Key == key {
            this.Hm[keyHash][index].Value = value
            return
        }
    }

    this.Hm[keyHash] = append(this.Hm[keyHash], &Node{
        Key: key,
        Value: value,
    })
}


func (this *MyHashMap) Get(key int) int {
    keyHash := hash(key)
    for _, element := range this.Hm[keyHash] {
        if element.Key == key {
            return element.Value
        }
    }

    return -1
}


func (this *MyHashMap) Remove(key int)  {
    keyHash := hash(key)
    for index, element := range this.Hm[keyHash] {
        if element.Key == key {
            this.Hm[keyHash][index].Value = -1
        }
    }
}