温故而知新--hashtable

哈希在实际使用中主要是当作私有内存，对数据进行插入和查找，哈希数据元素越多，操作的时候消耗的性能就越到，最明显的是当数据元素达到哈希的容量大小时，插入数据冲突概率会变大，并慢慢的退化为数组。

本例子中将会定义一个简单的hashtable。示例如下：

#include <iostream>
#include <list>
#include <string>
using namespace std;
class CHashTable{
public:
	typedef list<int>::iterator ListIter;
private:
	list<int> m_Container[3];//三个链表
	int HashFunction(const int& v) const;
	int m_Count;
public:
	CHashTable();
	~CHashTable();
	void Insert(const int& v);
	bool Find(const int& v);
	bool Delete(const int& v);    
	int Count() const;
};	
CHashTable::CHashTable(){
	m_Count = 0;
}
CHashTable::~CHashTable(){
	m_Count = 0;
	for(int i=0;i<3;i++){
		m_Container[i].clear();
	}
}
//哈希计算方法
int CHashTable::HashFunction(const int &v) const{
	return v%3;
}
//插入元素
void CHashTable::Insert(const int &v){
	m_Container[HashFunction(v)].push_back(v);
	m_Count++;
}
//查找元素
bool CHashTable::Find(const int &v){
	int iResKey = HashFunction(v);
	for(ListIter it = m_Container[iResKey].begin();it != m_Container[iResKey].end();it++){
		if(v == *it){
			return true;
		}
	}
	return false;
}
bool CHashTable::Delete(const int& v){
	int iResKey = HashFunction(v);
	for(ListIter it = m_Container[iResKey].begin();it != m_Container[iResKey].end();it++){
		if(v == *it){
			m_Container[iResKey].erase(it);
			m_Count --;
			return true;
		}
	}
	return false;
}
int CHashTable::Count() const{
	return m_Count;
}
int main(int argc, char *argv[]) {
	CHashTable myhash;
	//initialise the hash
	for(int i=0;i<10;i++){A
		myhash.Insert(i);
	}
	//return the size of hash
	std::cout<<"myhash size is:"<<myhash.Count()<<endl;
	
	std::cout<<"find the element 5: ";
	std::string strText = myhash.Find(5)? "yeah":"oh,no";
	std::cout<<strText<<std::endl;
	std::cout<<"del the element 5: "<<std::endl;
	myhash.Delete(5);
	std::cout<<"afther del find the element 5: ";
	strText = (myhash.Find(5)? "yeah":"oh,no");
	std::cout<<strText<<std::endl;
	std::cout<<"myhash size is:"<<myhash.Count()<<endl;
	return 0;
}