编程实现哈希存储算法的简单实现实例。

通过编写一个简单的哈希实例来加强对哈希算法的理解。下面实例包括存储与查找算法。拉链法解决冲突问题。

如果时间长了对哈希算法的理论知识不够了解，可以先阅读前面转载的两篇文档：

字符串哈希到整数函数，算法：http://blog.csdn.net/hzhsan/article/details/25552153

Hash算法冲突解决方法分析：http://blog.csdn.net/hzhsan/article/details/25555127

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <iostream>
#include <cstdlib>

#include <stdio.h>  
#include <string>  
using namespace std;

#define BUFF_COUNT 1000  
struct Student_info  
{  
string name;  
int age;  
}; 
  
struct Store_info  
{  
string key;
struct Student_info stu;
Store_info *pNext;  
Store_info()
{
pNext = NULL;
}

~Store_info()
{
Store_info* pTemp;
while (pNext != NULL)
{
pTemp = pNext;

delete pNext;
pNext = NULL;

pNext = pTemp->pNext;
}
}
};

Store_info *buff;

unsigned int BKDRHash(char *str)  
{  
unsigned int seed = 131; // 31 131 1313 13131 131313 etc..  
unsigned int hash = 0;  
while (*str)  
{  
hash = hash * seed + (*str++);  
} 
 
return (hash & 0x7FFFFFFF);  
}  
  
bool Hash_set(string key, const Student_info& student)  
{    
unsigned int hash_index =  BKDRHash((char*)key.c_str())%BUFF_COUNT;  
  
Store_info *pStore = &buff[hash_index];  
while ((pStore->key != key) && (pStore->pNext != NULL)) // if some key exists, store to the link list  
{  
pStore = pStore->pNext;  
}  
  
if (pStore->key == key)  
{  
pStore->stu = student;  
return true;  
}  
  
Store_info *pNewStore = new Store_info();  
pNewStore->key = key;  
pNewStore->stu = student;  
  
pStore->pNext = pNewStore;  
return true;  
}  
  
Student_info* Hash_get(string key)  
{  
unsigned int hash_index =  BKDRHash((char*)key.c_str())%BUFF_COUNT;  
Store_info *pStore = &buff[hash_index];  
if ((pStore->key != key) && (pStore->pNext != NULL))  
{  
pStore = pStore->pNext;  
}  
  
if (pStore->key == key)  
{  
return &pStore->stu;  
}  

return NULL;
}  

int main(int argc, char *argv[])
{
buff = new Store_info[BUFF_COUNT];

Student_info stu1;  
stu1.name = “hu”;  
stu1.age = 11;  
Hash_set(“key1”, stu1);  
  
Student_info stu2 = stu1;  
stu2.age = 22;  
Hash_set(“key2”, stu2);  
  
Student_info stu3 = stu1;  
stu3.age = 33;  
Hash_set(“key3”, stu3);  
  
Student_info *pstu = Hash_get(“key2”);
if (pstu == NULL)  
{  
printf(“ERROR:Get NULL\n”);  
}  
else  
{  
printf(“name:%s\nage:%d\n”,pstu->name.c_str(),pstu->age);  
}

delete []buff;

return EXIT_SUCCESS;
}

原文地址：http://blog.csdn.net/hzhsan/article/details/25567679