【C++之unordered_set和unordered_map的模拟实现】

C++之unordered_set和unordered_map的模拟实现

前言：
前面篇章学习了C++对unordered_set和unordered_map的认识和应用，接下来继续学习，C++的unordered_set和unordered_map模拟实现等知识。
/知识点汇总/

1、unordered_set的模拟实现

#define _CRT_SECURE_NO_WARNINGS 1

#include "HashBucket.h"

namespace bit1
{
	template<class K, class Hash = HashFunc<K>>//class Hash = HashFunc<K>修改参数在这里传入
	class unordered_set
	{
		struct SetKeyOfT
		{
			const K& operator()(const K& key)
			{
				return key;
			}
		};
	public:
		//迭代器
		typedef typename HashTable<K,const K, SetKeyOfT, Hash>::Iterator iterator;
		typedef typename HashTable<K, const K, SetKeyOfT, Hash>::const_Iterator const_iterator;

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

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

		const_iterator begin() const
		{
			return _ht.Begin();
		}

		const_iterator end() const
		{
			return _ht.End();//这里报错，是因为End()中的返回值，this指针问题
		}

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

		iterator find(const K& key)
		{
			return _ht.Find(key);
		}

		bool erase(const K& key)
		{
			return _ht.Erase(key);
		}

	private:
		//HashTable<K, V> _ht;
		HashTable<K,const K, SetKeyOfT, Hash> _ht;//+const
	};

	void test_unordered_set()
	{
		unordered_set<int> s;
		s.insert(31);
		s.insert(11);
		s.insert(5);
		s.insert(15);
		s.insert(25);

		unordered_set<int>::iterator it = s.begin();
		while (it != s.end())
		{
			//*it += 1;//set是不能被修改的，需要const修饰
			cout << *it << " ";
			++it;
		}
		cout << endl;

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

	//const迭代器
	void Func(const unordered_set<int>& s)
	{
		unordered_set<int>::iterator it = s.begin();
		while (it != s.end())
		{
			//*it = 1;
			cout << *it << " ";
			++it;
		}
		cout << endl;
	}
}
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2、unordered_map的模拟实现

#define _CRT_SECURE_NO_WARNINGS 1

#include "HashBucket.h"

namespace bit1
{
	template<class K, class V,class Hash = HashFunc<K>>
	class unordered_map
	{
		struct MapKeyOfT
		{
			const K& operator()(const pair<K, V>& kv)
			{
				return kv.first;
			}
		};
	public:
		typedef typename HashTable<K, pair<const K, V>, MapKeyOfT, Hash>::Iterator iterator;

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

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

		V& operator[](const K& key)
		{
			pair<iterator, bool> ret = insert(make_pair(key, V()));
			return ret.first->second;//报错发现->还没有写
		}

		// 21:15
		pair<iterator, bool> insert(const pair<K, V>& kv)
		{
			return _ht.Insert(kv);
		}
	private:
		HashTable<K, pair<const K, V>, MapKeyOfT, Hash> _ht;
	};

	void test_unordered_map()
	{
		string arr[] = { "苹果", "西瓜", "苹果", "西瓜", "苹果", "苹果", "西瓜",
	"苹果", "香蕉", "苹果", "香蕉","苹果","草莓", "苹果","草莓" };
		unordered_map<string, int> countMap;
		for (auto& e : arr)
		{
			countMap[e]++;
		}

		unordered_map<string, int>::iterator it = countMap.begin();
		while (it != countMap.end())
		{
			//it->first += 'x'; // key不能修改
			it->second += 1;  // value可以修改
			cout << it->first << ":" << it->second << endl;
			++it;
		}
		cout << endl;

		for (auto& kv : countMap)
		{
			cout << kv.first << ":" << kv.second << endl;
		}
		cout << endl;
	}
}
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