HashTable(哈希表分离链接法)

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哈希表的分离链接法其实就是个vector<type>容器 + 链表来实现的，其本质就是如果数值(mod)相等的话就插入到vector<type>的同一格，将相等的两个值依次存放在链表中，如果空间很小的话建议不要采用此方法，因为此方法的链表为双向链表，下面为分离链接法的代码:

#include<iostream>
#include<algorithm>
#include<string>
#include<vector>
#include<list>
using namespace std;
template<typename HashedObj>
class HashTable
{
public:explicit HashTable(int size = 101){theLists.resize(size);currentSize = size;}bool contains(const HashedObj & x) const;void makeEmpty();bool insert(const HashedObj & x);bool remove(const HashedObj & x);
private:vector<list<HashedObj> > theLists; // the array of Listsint currentSize;void rehash();int myHash(const HashedObj &x) const;
};
class Employee
{
public:const string &getName() const{return name;}bool operator== (const Employee &rhs) const{return getName() == rhs.getName();}bool operator!= (const Employee &rhs) const{return !(*this == rhs);}
private:string name;double salary;int senioity;
};
int hash(const string & key)
{int hashVal = 0;for(int i=0;i<key.length();i++){hashVal = hashVal * 37 + key[i];}return hashVal;
}
int hash(int key)
{return key;
}
int hash(const Employee & item)
{return hash(item.getName());
}
bool Prime(int res)         //散列表最好为素数
{for(int i=2;i<res/2;i++){if(res % i == 0){return true;break;}}return false;
}
int nextPrime(int num)
{while(1){if(Prime(num) == false){return num;break;}else{num++;}}
}
template<typename HashedObj>
int HashTable<HashedObj>::myHash(const HashedObj & x) const
{int hashVal = hash(x);hashVal %= theLists.size();  //theLists.size()为总容量if(hashVal < 0){hashVal += theLists.size();}return hashVal;
}
template<typename HashedObj>
void HashTable<HashedObj>::rehash()
{vector<list<HashedObj> > oldLists = theLists;theLists.resize(nextPrime(2 * theLists.size()));for(int j=0;j<theLists.size();j++){theLists[j].clear();}cout<<theLists.size()<<endl;currentSize = 0;for(int i=0;i<oldLists.size();i++)  //vector<>从上到下{typename list<HashedObj>::iterator itr = oldLists[i].begin(); //链表头到尾覆盖while(itr != oldLists[i].end())insert(*itr++);}
}
template<typename HashedObj>
void HashTable<HashedObj>::makeEmpty()
{for(int i=0;i<theLists.size();i++){theLists[i].clear();}
}
template<typename HashedObj>
bool HashTable<HashedObj>::contains(const HashedObj & x) const
{const list<HashedObj> &whichList = theLists[myHash(x)];return find(whichList.begin(),whichList.end(),x) != whichList.end();
}
template<typename HashedObj>
bool HashTable<HashedObj>::remove(const HashedObj &x)
{list<HashedObj> & whichList = theLists[myHash(x)];typename list<HashedObj>::iterator itr = find(whichList.begin(),whichList.end(),x);if(itr == whichList.end()){return false;}whichList.erase(itr);--currentSize;return true;
}
template<typename HashedObj>
bool HashTable<HashedObj>::insert(const HashedObj &x)
{list<HashedObj> & whichList = theLists[myHash(x)];if(find(whichList.begin(),whichList.end(),x) != whichList.end()){return false; // 如果已经存在}whichList.push_back(x);if(++currentSize >theLists.size())rehash();return true;
}
int main()
{HashTable<int> b;b.insert(1);b.insert(10);b.insert(100);b.insert(9);b.insert(69);b.insert(57);if(b.contains(100) && b.contains(57)){cout<<"yes"<<endl;}else{cout<<"no"<<endl;}if(b.insert(57)){cout<<"insert succeed!"<<endl;}else{cout<<"repeat!"<<endl;}if(b.remove(69)){cout<<"remove succeed!"<<endl;}else{cout<<"The element not exist in HashTable";}b.makeEmpty();if(b.contains(1) || b.contains(10) || b.contains(100)){cout<<"The HashTable is not empty!"<<endl;}else{cout<<"It is empty!"<<endl;}return 0;
}

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