平方探测哈希表

#include <vector>
#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

 


template <typename HashedObj>
class HashTable
{
public:
	explicit HashTable(int size=101)
	:theSize(nextPrime(size)),array(nextPrime(size))
	{
		makeEmpty();
	}

	bool contains(const HashedObj &x) const
	{
		return isActive(findPos(x));
	}

	void makeEmpty()
	{
		currentSize=0;
		for(auto &entry:array)
			entry.info=EMPTY;
	}

	bool insert(const HashedObj &x)
	{
		int currentPos=findPos(x);
		if(isActive(currentPos))
			return false;

		array[currentPos].element=x;
		array[currentPos].info=ACTIVE;

		if(++currentSize>array.size()/2)
			rehash();

		return true;
	}

	bool insert(HashedObj &&x)
	{
		int currentPos=findPos(x);
		if(isActive(currentPos))
			return false;

		array[currentPos].element=x;
		array[currentPos].info=ACTIVE;

		if(++currentSize>array.size()/2)
			rehash();

		return true;
	}


	bool remove(const HashedObj &x)
	{
		int currentPos=findPos(x);
		if(!isActive(currentPos))
			return false;

		array[currentPos].info=DELETED;
		return true;
	}

	void print()
	{
		for(auto HashEntry:array)
			if(HashEntry.info==ACTIVE)
				cout<<HashEntry.element<<endl;
	}
	enum EntryType{ACTIVE,EMPTY,DELETED};

private:
	struct HashEntry
	{
		HashedObj element;
		EntryType info;

		HashEntry(const HashedObj &e=HashedObj{ },EntryType i=EMPTY)
		:element(e),info(i)
		{ }

		HashEntry(HashedObj &&e,EntryType i=EMPTY)
		:element(e),info(i)
		{ }
	};

	vector<HashEntry> array;
	int currentSize;
	int theSize;

	bool isActive(int currentPos) const
	{
		return array[currentPos].info==ACTIVE;
	}

	int findPos(const HashedObj &x) const
	{
		int offset=1;
		int currentPos=myhash(x);
		while(array[currentPos].info!=EMPTY&&
			array[currentPos].element!=x)
		{
			currentPos+=offset;
			offset+=2;
			if(currentPos>=array.size())
				currentPos-=array.size();
		}
		return currentPos;
	}


	void rehash()
	{
		vector<HashEntry> oldArray=array;

		array.resize(nextPrime(2*oldArray.size()));
		for(auto &entry:array)
			entry.info=EMPTY;
		currentSize=0;
		for(auto &entry:oldArray)
			if(entry.info==ACTIVE)
				insert(std::move(entry.element));

	}

	int myhash(const HashedObj &x) const
	{
		int hashVal=0;
		for(auto &c:x)
			hashVal=131*hashVal+c;
		hashVal%=array.size();
		if(hashVal<0)
			hashVal+=theSize;
		return hashVal;
	}
	bool isPrime(int num)    
	{    
    	if (num == 2 || num == 3)       
        	return true;       
    	if (num % 6 != 1 && num % 6 != 5)    
        	return false;    
   
    	for (int i = 5; i*i <= num; i += 6)      
        	if (num % i == 0 || num % (i+2) == 0)      
           	 return false;    
    	return true;    
	}  
  
	int nextPrime(int n)  
	{  
    	bool state=isPrime(n);  
    	while(!state)  
        	state=isPrime(++n);  
    	return n;  
	} 

};


int main()
{
	HashTable<string> hash;
	hash.insert("this");
	hash.print();

}