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

// 假设现在要实现一个存储学生信息的hash内存表，封装hash值的存储与获取，并通过拉链法解决地址冲突。#include <stdio.h>#include <string>using std::string;// 定义hash表初始开辟内存空间元素的个数。这里只用1000做测试。#define BUFF_COUNT 1000// 学生信息结构struct Student_info{        string name;        int age;};// 实际存储元素结构struct Store_info{       string key;                                     // 将key做存储，目的是为了判断冲突问题        struct Student_info stu;                        // 实际需要存储的数据信息        Store_info *pNext;                              // 当发生冲突时用以形成链表        Store_info():pNext(NULL){}};Store_info *buff;		//之后用于申请大片存储数据的内存// BKDRHash函数，得到一个字符串所对应的整型，用于计算hash值。此函数见：http://blog.csdn.net/hzhsan/article/details/25552153unsigned 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){        // 计算实际的hash值，除以BUFF_COUNT是为了使hash的映射到一个较小的范围。        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(){        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("key2", 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);        }        printf("end~\n");        delete[] buff;        return 0;}

如有任何问题，希望各位指正，谢谢。