哈希表hashtables算法

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#pragma once#include<iostream>#include<string>using namespace std;enum Status{    EMPTY,   //为空    EXIST,   //存在pair    DELETED,  //存在过pair，但是被删除了};//一个算法将字符串转化为整数static size_t BKDRHash(const char * str){    unsigned int seed = 131; // 31 131 1313 13131 131313    unsigned int hash = 0;    while (*str)    {        hash = hash * seed + (*str++);    }    return (hash & 0x7FFFFFFF);}//为string定制的仿函数struct __HashFuncS{    size_t operator()(const string& str)    {        return BKDRHash(str.c_str());    }};//对 int型struct __HashFuncInt{    size_t operator()(const int& key)    {        return key;    }};//这里用的是除留余数法构建哈希表，并用开放地址法-二次探测 处理哈希冲突，载荷因子限制为0.7template <class K, class V, class _HashFunc = __HashFuncInt >class HashTables{    static const size_t InitialCapacity = 10;public:    HashTables(size_t capacity = InitialCapacity)        : _status(new Status[capacity])        , _tables(new pair<K, V>[capacity])        , _size(0)        , _capacity(capacity)    {        for (size_t i = 0; i < capacity; ++i)        {            _status[i] = EMPTY;        }    }    void CheckCapacity()    {        if (_size * 10 / _capacity == 7)        {            size_t newcapacity = 2 * _capacity;            HashTables ht(newcapacity);            size_t i = 0;            for (; i < _capacity; ++i)            {                if (_status[i] == EXIST)                    ht.Insert(_tables[i].first, _tables[i].second);            }            swap(_tables, ht._tables);            swap(_status ,ht._status);            swap(_size, ht._size);            swap(_capacity, ht._capacity);        }    }    pair<K, V>*  Find(const K& key)    {        size_t i = 0;        size_t index = HashFunc(key, i);        while (_status[index]!= EMPTY)        {            if (_tables[index].first == key)            {                return &_tables[index];            }            index = HashFunc(key, ++i);        }        return NULL;    }    bool Insert(const K& key,const V& value)    {        if (Find(key))            return false;        CheckCapacity();        size_t i = 0;        size_t index = HashFunc(key, i);        while (_status[index]==EXIST)        {            index = HashFunc(key, ++i);        }        _tables[index].first = key;        _tables[index].second = value;        _status[index] = EXIST;        _size++;        return true;    }    void print()    {        for (size_t i = 0; i < _capacity; ++i)        {            if (_status[i] == EXIST)            {                cout <<i<< "   key: " << _tables[i].first << "      value: " << _tables[i].second << endl;            }            else            {                cout << i << "   no" << endl;            }        }    }private:    size_t HashFunc(const K& key, size_t i)    {        return (_HashFunc()(key) + i*i) % _capacity;    }protected:    Status* _status;    pair<K, V>* _tables;    size_t _size;    size_t _capacity;};

下面给一个测试用例：

#include"hashtable.h"void test1(){    HashTables<int, int> ht;    int a[] = { 89, 18, 49, 58, 9 };    for (size_t i = 0; i < sizeof(a) / sizeof(int); ++i)    {        ht.Insert(a[i], i);    }    ht.print();}void test2(){    HashTables<string,string,__HashFuncS> ht2;    ht2.Insert("sort", "排序");    ht2.Insert("sort1", "排序1");    ht2.Insert("sort2", "排序2");    ht2.Insert("sort3", "排序3");    ht2.print();}int main(){    test2();    system("pause");    return 0;}

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