Design Your 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.

Example:
MyHashMap hashMap = new MyHashMap();
hashMap.put(1, 1);
hashMap.put(2, 2);
hashMap.get(1); // returns 1
hashMap.get(3); // returns -1 (not found)
hashMap.put(2, 1); // update the existing value
hashMap.get(2); // returns 1
hashMap.remove(2); // remove the mapping for 2
hashMap.get(2); // returns -1 (not found)

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.

Runtime:240ms Usage:40MB

static const auto fasterIO = [](){
    // use printf and scanf instead of cout and cin
    std::ios::sync_with_stdio(false);
    // untie cin and cout
    std::cin.tie(nullptr);
    return nullptr;
}();

class MyHashMap {
public:
    /** Initialize your data structure here. */
    MyHashMap() {
        
    }
    
    /** value will always be non-negative. */
    void put(int key, int value) {
        int i = 0;
        for(i = 0; i < vec.size() ;i++)
        {
            if(vec[i].key == key)
            {
                vec[i].value = value;
                break;
            }
        }
        if(i == vec.size())
        {
            Member_T m{key,value};
            vec.push_back(m);
        }
    }
    
    /** 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) {
        if(key < 0)
            return -1;
        
        for(int i = 0; i < vec.size() ; i++)
        {
            if(vec[i].key == key)
            {
                return vec[i].value;
            }
        }

        return -1;
    }
    
    /** Removes the mapping of the specified value key if this map contains a mapping for the key */
    void remove(int key) {
        for(int i = 0; i < vec.size();i++)
        {
            if(vec[i].key == key)
            {
                vec.erase(vec.begin() + i);
            }
        }
    }
private:
    typedef struct{
        int key;
        int value;
    }Member_T;
    vector<Member_T> vec;
};

Runtime:96ms Usage:48MB

static const auto fasterIO = [](){
    // use printf and scanf instead of cout and cin
    std::ios::sync_with_stdio(false);
    // untie cin and cout
    std::cin.tie(nullptr);
    return nullptr;
}();

class MyHashMap {
public:
    /** Initialize your data structure here. */
    MyHashMap() {
        int size = 128;
        hash.resize(size,vector<paII>());
    }
    
    /** value will always be non-negative. */
    void put(int key, int value) {
        int hash_value = key % N;
        if(hash_value > hash.size())
        {
            changeSize(hash_value);
        }
        auto i = find_if(hash[hash_value].begin(), hash[hash_value].end(),\
                        [key](const paII& p) -> bool{
                            return p.first == key;
                        });
        if(i != hash[hash_value].end())
        {
            hash[hash_value][i - hash[hash_value].begin()].second = value;
        }
        else
        {
            hash[hash_value].push_back(paII(key,value));
        }
    }
    
    /** 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 hash_value = key % N;
        if(hash_value > hash.size())
        {
            return -1;
        }
        auto i = find_if(hash[hash_value].begin(),hash[hash_value].end(),\
                        [key](const paII& p) ->bool{
                            return p.first == key;
                        });
        if(i != hash[hash_value].end())
        {
            return hash[hash_value][i - hash[hash_value].begin()].second;
        }
        else
        {
            return -1;
        }
    }
    
    /** Removes the mapping of the specified value key if this map contains a mapping for the key */
    void remove(int key) {
        put(key,-1);
    }
private:
    void changeSize(int hash_value)
    {
        int i = 128;
        while(i < hash_value)
            i <<= 1;
        hash.resize(i,vector<paII>());
    }   
    
    typedef pair<int,int> paII;
    vector< vector<paII>> hash;
    unsigned long long N = 1e4+7;
};