C++实现unordermap容器和unorderset容器

代码如下:

#include 
#include 
using namespace std;


template<typename K,typename V,typename KeyOfValue>
class HashTable;//声明

template<typename V>
struct HashNode
{
     
	typedef HashNode<V> Node;
	V _val;
	Node * _next;

	HashNode(const V & val):_val(val),_next(nullptr){
     }
};

template<typename K,typename V,typename KeyOfValue>
struct HashIterator
{
     
	typedef HashNode<V> Node;
	typedef HashIterator<K, V, KeyOfValue> Self;
	typedef HashTable<K, V, KeyOfValue>HT;
	Node *_node;
	HT * _hPtr;

	HashIterator(Node *node,HT *hPtr):_node(node),_hPtr(hPtr){
     }

	V &operator*()
	{
     
		return _node->_val;
	}

	V *operator->()
	{
     
		return &_node->_val;
	}

	bool operator!=(const Self & it)
	{
     
		return _node != it._node;
	}

	Self & operator++()
	{
     
		if (_node->_next)
		{
     
			_node = _node->_next;
		}
		else
		{
     
			KeyOfValue kov;
			size_t idx = kov(_node->_val) % _hPtr->_ht.size();

			++idx;
			for (; idx < _hPtr->_ht.size(); idx++)
			{
     
				if (_hPtr->_ht[idx])
				{
     
					_node = _hPtr->_ht[idx];
					break;
				}
			}

			if (idx == _hPtr->_ht.size()) _node = nullptr;
		}
		return *this;
	}

};

template<typename K,typename V,typename KeyOfValue>
class HashTable
{
     
public:
	typedef HashIterator<K, V, KeyOfValue> iterator;
	typedef HashNode<V> Node;

	template<typename K,typename V,typename KeyOfValue>
	friend struct HashIterator;

	HashTable(int n = 10):_ht(n),_size(0){
     }

	iterator begin()
	{
     
		for (size_t i = 0; i < _ht.size(); i++)
		{
     
			if (_ht[i])
			{
     
				return iterator(_ht[i], this);
			}
		}
		return iterator(nullptr, this);
	}

	iterator end()
	{
     
		return iterator(nullptr, this);
	}

	pair<iterator, bool> insert(const V & val)
	{
     

		//0.检查容量
		checkCapacity();

		KeyOfValue kov;

		//1.计算hash位置
		int idx = kov(val) % _ht.size();

		//2.查找
		Node *cur = _ht[idx];
		while (cur)
		{
     
			if (kov(cur->_val) == kov(val)) return make_pair(iterator(cur, this), false);
			cur = cur->_next;
		}

		//3.插入--头插
		cur = new Node(val);
		cur->_next = _ht[idx];
		_ht[idx] = cur;
		++_size;
		return make_pair(iterator(cur, this), true);
	}

	void checkCapacity()
	{
     
		if (_size == _ht.size())
		{
     
			int newC = _size == 0 ? 10 : 2 * _size;

			vector<Node *>newHt(newC);

			KeyOfValue kov;

			for (size_t i = 0; i < _ht.size(); i++)
			{
     
				Node *cur = _ht[i];

				while (cur)
				{
     
					Node *next = cur->_next;

					int idx = kov(cur->_val) % newHt.size();

					cur->_next = newHt[idx];
					newHt[idx] = cur;

					cur = next;
				}

				_ht[i] = nullptr;
			}

			swap(_ht, newHt);
		}
	}

private:
	vector<Node *> _ht;
	int _size;
};


template<typename K>
class UnorderedSet
{
     
	struct SetKeyOfValue
	{
     
		const K & operator()(const K & key)
		{
     
			return key;
		}
	};

public:
	typedef typename  HashTable<K, K, SetKeyOfValue>::iterator iterator;

	pair<iterator, bool> insert(const K& key)
	{
     
		return _ht.insert(key);
	}

	iterator begin()
	{
     
		return _ht.begin();
	}

	iterator end()
	{
     
		return _ht.end();
	}

private:
	HashTable<K, K, SetKeyOfValue> _ht;
};


template<typename K,typename V>
class UnorderedMap
{
     
	struct MapKeyOfValue
	{
     
		const K& operator()(const pair<K, V> & val)
		{
     
			return val.first;
		}
	};

public:
	typedef typename HashTable<K, pair<K, V>, MapKeyOfValue>::iterator iterator;

	pair<iterator, bool > insert(const pair<K, V> & val)
	{
     
		return _ht.insert(val);
	}

	iterator begin() {
     
		return _ht.begin();
	}

	iterator end()
	{
     
		return _ht.end();
	}

	V & operator[](const K& key)
	{
     
		pair<iterator, bool> ret = _ht.insert(make_pair(key, V()));
		return ret.first->second;
	}

private:
	HashTable<K, pair<K, V>, MapKeyOfValue> _ht;
};

int main()
{
     
	UnorderedSet<int>s;
	s.insert(1);
	s.insert(123);
	s.insert(123412);
	s.insert(12);
	s.insert(1132);
	s.insert(1131);
	s.insert(436);
	s.insert(786);
	s.insert(13);
	s.insert(7965);
	s.insert(7653);
	s.insert(645);
	s.insert(324);

	UnorderedSet<int>::iterator it1 = s.begin();
	while (it1 != s.end())
	{
     
		cout << *it1 << " ";
		++it1;
	}
	cout << endl;

	for (const auto & e : s)
	{
     
		cout << e << " ";
	}
	cout << endl;


	UnorderedMap<int, int>m;
	m.insert(make_pair(1, 1));
	m[2] = 2;
	m[3] = 3;

	UnorderedMap<int, int>::iterator it2 = m.begin();
	while (it2 != m.end())
	{
     
		cout << it2->first << "--->" << it2->second << endl;
		++it2;
	}
	cout << "--------------------" << endl;

	m[2] = 20;
	for (auto & p : m)
	{
     
		cout << p.first << "--->" << p.second << endl;
	}
	return 0;
}

测试结果: