哈希表的实现

来源：互联网发布：java网站实例编辑：程序博客网时间：2024/05/05 02:11
#include <iostream>#include <vector>#include <string>using namespace std;enum Status  {EMPTY,      EXIST,      DELETE,};    template<class K,class V>struct KVNode  {K _key;      V _value;      Status _status;      KVNode(const K& key=K(),const V& value=V()) :_key(key)          ,_value(value)          ,_status(EMPTY)          {}  };    template<class K>  struct __HashFunc  {   size_t operator()(const K& key)       {   return key;       }  };//特化  template<>  struct __HashFunc<string>  {  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);  }  size_t operator()(const string& str)  {return BKDRHash(str.c_str());  }};template<class K,class V,class HashFunc=__HashFunc<K>>  class HashTable {  typedef KVNode<K,V> Node;  public:  HashTable()  :_size(0)  {  _tables.resize(_GetPrime(0));  }  HashTable(const HashTable<K,V,HashFunc>& hash)  {  size_t size=hash._tables.size();          _tables.resize(size);          for (size_t i=0;i<_tables.size();++i)          {  if (hash._tables[i]._status == EXIST)  {  _tables[i]._key=hash._tables[i]._key;                  _tables[i]._value=hash._tables[i]._value;                  _tables[i]._status=hash._tables[i]._status;  }  }  _size=hash._size;}  HashTable<K,V,HashFunc>& operator=(const HashTable<K,V,HashFunc>& hash)  {  if (this != &hash)  {  HashTable<K,V,HashFunc> tmp(hash);  _Swap(tmp);  }  return *this;  }  public:  bool Insert(const K& key,const V& value)  {  _CheckSize();          size_t index=_GetPosition(key);          while (_tables[index]._status == EXIST)  {  if (_tables[index]._key == key)  {  return false;}  ++index;              if(index == _tables.size())  index=0;  }  _tables[index]._key=key;_tables[index]._value=value;  _tables[index]._status=EXIST;          _size++;          return true;  }      void Remove(const K& key)       //伪删除法  {  Node *ret=Find(key);  if (ret != NULL)  {  ret->_status=DELETE;  _size--;  }  }  Node *Find(const K& key)  {  size_t index=_GetPosition(key);          size_t src=index;          while (_tables[index]._status != EMPTY)          {  if (_tables[index]._key == key)              {  if (_tables[index]._status == DELETE) return NULL;                  else  return &_tables[index];  }              ++index;              if(index == src)  break;  }  return NULL;}  void Print()  {  for (size_t i=0;i<_tables.size();++i)  {  if (_tables[i]._status == EXIST)  {  cout<<_tables[i]._key<<"  "<<_tables[i]._status<<endl;  }}  cout<<endl; }  protected:  void _CheckSize()      {  if (_tables.size() == 0 || _size*10/_tables.size() >= 8)          {  size_t NewSize=_GetPrime(_tables.size());              HashTable<K,V,HashFunc> hashTable;         //现代的写法              hashTable._tables.resize(NewSize);              for (size_t i=0;i<_tables.size();++i)  {  if(_tables[i]._status == EXIST)  {  hashTable.Insert(_tables[i]._key,_tables[i]._value);  }  }   _Swap(hashTable);  }  }  void _Swap(HashTable<K,V,HashFunc> hash){  _tables.swap(hash._tables);  swap(_size,hash._size);  }  size_t _GetPrime(size_t num)  {  const int _PrimeSize= 28;         //素数表         static const unsigned long _PrimeList[_PrimeSize] =     {     53ul, 97ul, 193ul, 389ul, 769ul,             1543ul, 3079ul, 6151ul, 12289ul, 24593ul,             49157ul, 98317ul, 196613ul, 393241ul,             786433ul,             1572869ul, 3145739ul, 6291469ul, 12582917ul,             25165843ul,             50331653ul, 100663319ul, 201326611ul, 402653189ul,             805306457ul,            1610612741ul, 3221225473ul, 4294967291ul     };         for (size_t i=0;i<_PrimeSize;++i)     {     if(_PrimeList[i] > num)     return _PrimeList[i];     else   continue;     }     return _PrimeList[_PrimeSize-1];  }  size_t _GetPosition(const K& key)        //除留余数法  {  HashFunc hf;  return hf(key)%_tables.size();  }  protected:  vector<Node> _tables;      size_t _size;  };
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