数据结构与算法分析习题5.20答案

template 
class Pair
{
private:
	HashedObj key;
	Object def;
public:
	explicit Pair(const HashedObj& k = HashedObj{}, const Object& de = Object{}) :
		key(k), def(de) {}
	const HashedObj& first() const
	{
		return key;
	}
	const Object& second() const
	{
		return def;
	}
	bool operator == (const Pair& rhs) const
	{
		return key == rhs.key;
	}
	bool operator != (const Pair& rhs) const
	{
		return !(*this == rhs);
	}
};


template 
class Hash
{
public:
	size_t operator()(const Key& key) const
	{
	
	}
};

template <>
class Hash >
{
public:
	size_t operator() (const Pair& rhs) const
	{
		static unordered_set::hasher hf;
		return hf(rhs.first());
		
	}
};




template 
class Dictionary
{
private:
	unordered_set, Hash> > items;
public:
	Dictionary()
	{
	}
	void insert(const HashedObj& k, const Object& definition)
	{
		items.insert(Pair(k, definition));
	}
	const Object& lookup(const HashedObj& key) const
	{
		auto iter = items.find(Pair(key));
		return (*iter).second();
	}
	bool isEmpty()const
	{
		return items.empty();
	}
	void makeEmpty()
	{
		items.clear();
	}

};

示例

Dictionary dic;
	for (int i = 0; i < 1000; i++)
	{
		dic.insert(to_string(i), i + 1);
	}
	cout << dic.lookup(to_string(888)) << endl;