拉链法

class MyHashMap 
{
public:
    const static int N = 20011;
    vector<list<pair<int,int>>> hash;

    MyHashMap() 
    {
        hash = vector<list<pair<int,int>>>(N);
    }

    list<pair<int,int>>::iterator find(int key)
    {
        int t = key % N;
        auto it = hash[t].begin();
        for (; it != hash[t].end(); it ++ )
            if (it->first == key)
                break;
        return it;
    }

    void put(int key, int value) 
    {
        int t = key % N;
        auto it = find(key);
        if (it == hash[t].end())
            hash[t].push_back(make_pair(key, value));
        else
            it->second = value;
    }

    int get(int key) 
    {
        int t = key % N;
        auto it = find(key);
        if (it == hash[key % N].end()) return -1;
        return it->second;
    }

    void remove(int key) 
    {
        int t = key % N;
        auto it = find(key);
        if (it != hash[t].end())
            hash[t].erase(it);
    }
};