706. Design HashMap

Design a HashMap without using any built-in hash table libraries.

To be specific, your design should include these functions:

• put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.
• get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
• remove(key) : Remove the mapping for the value key if this map contains the mapping for the key.

Note:

• All keys and values will be in the range of [0, 1000000].
• The number of operations will be in the range of [1, 10000].
• Please do not use the built-in HashMap library.

class MyHashMap {
private:
    vector<map<int, int>> myHashMap;
    
    int hash(int key) {
        return key % 31;
    }
public:
    /** Initialize your data structure here. */
    MyHashMap() {
        myHashMap = vector<map<int, int>> (31, map<int,int>());
    }

    /** value will always be non-negative. */
    void put(int key, int value) {
        int index = hash(key);
        myHashMap[index][key] = value;
        return;
    }

    /** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key */
    int get(int key) {
        int index = hash(key);
        if(myHashMap[index].count(key))
            return myHashMap[index][key];
        return -1;
    }

    /** Removes the mapping of the specified value key if this map contains a mapping for the key */
    void remove(int key) {
        int index = hash(key);
        if(myHashMap[index].count(key))
            myHashMap[index][key] = -1;
        return;
    }
};

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