由于hashmap不是c++ stl中标准实现，这样在跨平台使用时就可能会出现问题，于是想到自己实现一个hashmap

hash算法使用开链法解决hash冲突，主要实现了添加，删除，查找几个方法

头文件如下hashmap.h

#ifndef _HASHMAP_H_#define _HASHMAP_H_template
     
      class HashNode{public:    Key    _key;    Value  _value;    HashNode *next;    HashNode(Key key, Value value)    {        _key = key;        _value = value;        next = NULL;    }    ~HashNode()    {    }    HashNode& operator=(const HashNode& node)    {        _key  = node._key;        _value = node._value;        next = node.next;        return *this;    }};template 
      
       class HashMap{public:    HashMap(int size);    ~HashMap();    bool insert(const Key& key, const Value& value);    bool del(const Key& key);    Value& find(const Key& key);    Value& operator [](const Key& key);private:    HashFunc hash;    EqualKey equal;    HashNode
       
         **table;    unsigned int _size;    Value ValueNULL;};template 
        
         HashMap
         
          ::HashMap(int size) : _size(size),hash(),equal(){
        table = new HashNode
          
           *[_size]; for (unsigned i = 0; i < _size; i++) table[i] = NULL;}template 
           
            HashMap
            
             ::~HashMap(){ for (unsigned i = 0; i < _size; i++) { HashNode
             
               *currentNode = table[i]; while (currentNode) { HashNode
              
                *temp = currentNode; currentNode = currentNode->next; delete temp; } } delete table;}template 
               
                bool HashMap
                
                 ::insert(const Key& key, const Value& value){ int index = hash(key)%_size; HashNode
                 
                   * node = new HashNode
                  
                   (key,value); node->next = table[index]; table[index] = node; return true;}template 
                   
                    bool HashMap
                    
                     ::del(const Key& key){ unsigned index = hash(key) % _size; HashNode
                     
                       * node = table[index]; HashNode
                      
                        * prev = NULL; while (node) { if (node->_key == key) { if (prev == NULL) { table[index] = node->next; } else { prev->next = node->next; } delete node; return true; } prev = node; node = node->next; } return false;}template 
                       
                        Value& HashMap
                        
                         ::find(const Key& key){ unsigned index = hash(key) % _size; if (table[index] == NULL) return ValueNULL; else { HashNode
                         
                           * node = table[index]; while (node) { if (node->_key == key) return node->_value; node = node->next; } }}template 
                          
                           Value& HashMap
                           
                            ::operator [](const Key& key){ return find(key);}#endif
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

测试代码

//首先要定义hash函数与比较函数class HashFunc{public:    int operator()(const string & key )    {        int hash = 0;        for(int i = 0; i < key.length(); ++i)        {            hash = hash << 7 ^ key[i];        }        return (hash & 0x7FFFFFFF);    }};class EqualKey{public:    bool operator()(const string & A, const string & B)    {        if (A.compare(B) == 0)            return true;        else            return false;    }};测试用例int main(){    HashMap
     
       hashmap(100);    hashmap.insert("hello", "world");    hashmap.insert("why", "dream");    hashmap.insert("c++", "good");    hashmap.insert("welcome", "haha");        cout << "after insert:" << endl;    cout << hashmap.find("welcome").c_str() << endl;    cout << hashmap.find("c++").c_str() << endl;    cout << hashmap["why"].c_str() << endl;    cout << hashmap["hello"].c_str() << endl;    if (hashmap.del("hello"))        cout << "remove is ok" << endl;    //remove is ok    cout << hashmap.find("hello").c_str() << endl; //not exist print NULL    hashmap["why"] = "love";    cout << hashmap["why"].c_str() << endl;    return 0;}