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哈希表(HashTable)的简单实现[C语言](原创)

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简单实现了哈希表的插入和查找功能,简要说明如下:
1、数据结构:


struct HashNode
{
    char* sKey;     //键
    int nValue;      //值
    HashNode* pNext; //当Hash值冲突时,指向HASH值相同的下一个节点。
}
HashNode* hashTable[HASH_TABLE_MAX_SIZE]; //哈希表的数组
int hash_table_size;       //哈希表中元素的个数
  

2、函数: void hash_table_init() 初始化哈希表
void hash_table_insert(const char* skey, int nvalue) 向哈希表中插入键位skey,值为nvalue的键值对。
当skey已经在哈希表中时,忽略该键值对。


void hash_table_remove(const char* skey) 从哈希表中删除键值对。
HashNode* hash_table_lookup(const char* skey) 查找键值为skey的节点。当找到时,返回对应的HashNode指针,没有找到时,返回NULL。
void hash_table_release() 释放哈希表的内存空间。

C语言实现的哈希表(HashTable)源码如下:

/*
 * Author: puresky
 * Date: 2008/01/08
 * Purpose: a simple implementation of HashTable in C
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

/*=================hash table start=========================================*/

#define HASH_TABLE_MAX_SIZE 10000
typedef struct HashNode_Struct HashNode;

struct HashNode_Struct
{
    char* sKey;
    int nValue;
    HashNode* pNext;
};

HashNode* hashTable[HASH_TABLE_MAX_SIZE]; //hash table data strcutrue
int hash_table_size;  //the number of key-value pairs in the hash table!

//initialize hash table
void hash_table_init()
{
    hash_table_size = 0;
    memset(hashTable, 0, sizeof(HashNode*) * HASH_TABLE_MAX_SIZE);
}


//string hash function
unsigned int hash_table_hash_str(const char* skey)
{
    const signed char *p = (const signed char*)skey;
    unsigned int h = *p;
    if(h)
    {
        for(p += 1; *p != '\0'; ++p)
            h = (h << 5) - h + *p;
    }
    return h;
}

//insert key-value into hash table
void hash_table_insert(const char* skey, int nvalue)
{
    if(hash_table_size >= HASH_TABLE_MAX_SIZE)
    {
        printf("out of hash table memory!\n");
        return;
    }

    unsigned int pos = hash_table_hash_str(skey) % HASH_TABLE_MAX_SIZE;

    HashNode* pHead =  hashTable[pos];
    while(pHead)
    {
        if(strcmp(pHead->sKey, skey) == 0)
        {
            printf("%s already exists!\n", skey);
            return ;
        }
        pHead = pHead->pNext;
    }

    HashNode* pNewNode = (HashNode*)malloc(sizeof(HashNode));
    memset(pNewNode, 0, sizeof(HashNode));
    pNewNode->sKey = (char*)malloc(sizeof(char) * (strlen(skey) + 1));
    strcpy(pNewNode->sKey, skey);
    pNewNode->nValue = nvalue;

    pNewNode->pNext = hashTable[pos];
    hashTable[pos] = pNewNode;


    hash_table_size++;
}
//remove key-value frome the hash table
void hash_table_remove(const char* skey)
{
    unsigned int pos = hash_table_hash_str(skey) % HASH_TABLE_MAX_SIZE;
    if(hashTable[pos])
    {
        HashNode* pHead = hashTable[pos];
        HashNode* pLast = NULL;
        HashNode* pRemove = NULL;
        while(pHead)
        {
            if(strcmp(skey, pHead->sKey) == 0)
            {
                pRemove = pHead;
                break;
            }
            pLast = pHead;
            pHead = pHead->pNext;
        }
        if(pRemove)
        {
            if(pLast)
                pLast->pNext = pRemove->pNext;
            else
                hashTable[pos] = NULL;

            free(pRemove->sKey);
            free(pRemove);
        }
    }
}

//lookup a key in the hash table
HashNode* hash_table_lookup(const char* skey)
{
    unsigned int pos = hash_table_hash_str(skey) % HASH_TABLE_MAX_SIZE;
    if(hashTable[pos])
    {
        HashNode* pHead = hashTable[pos];
        while(pHead)
        {
            if(strcmp(skey, pHead->sKey) == 0)
                return pHead;
            pHead = pHead->pNext;
        }
    }
    return NULL;
}

//print the content in the hash table
void hash_table_print()
{
    printf("===========content of hash table=================\n");
    int i;
    for(i = 0; i < HASH_TABLE_MAX_SIZE; ++i)
        if(hashTable[i])
        {
            HashNode* pHead = hashTable[i];
            printf("%d=>", i);
            while(pHead)
            {
                printf("%s:%d  ", pHead->sKey, pHead->nValue);
                pHead = pHead->pNext;
            }
            printf("\n");
        }
}

//free the memory of the hash table
void hash_table_release()
{
    int i;
    for(i = 0; i < HASH_TABLE_MAX_SIZE; ++i)
    {
        if(hashTable[i])
        {
            HashNode* pHead = hashTable[i];
            while(pHead)
            {
                HashNode* pTemp = pHead;
                pHead = pHead->pNext;
                if(pTemp)
                {
                    free(pTemp->sKey);
                    free(pTemp);
                }

            }
        }
    }
}

/* ===============================hash table end=========================*/


/* ============================test function ============================*/
#define MAX_STR_LEN 20
#define MIN_STR_LEN 10
void rand_str(char r[])
{
    int i;
    int len = MIN_STR_LEN + rand() % (MAX_STR_LEN - MIN_STR_LEN);
    for(i = 0; i < len - 1; ++i)
        r[i] = 'a' + rand() % ( 'z' - 'a');
    r[len - 1] = '\0';
}

int main(int argc, char** argv)
{
    srand(time(NULL));
    hash_table_init();
    printf("insert testing.........\n");
    int n = 10;
    const char *key1 = "aaammd";
    const char *key2 = "xzzyym";
    const char *key3 = "cdcded";

    hash_table_insert(key1, 110);
    hash_table_insert(key2, 220);
    hash_table_insert(key3, 330);
    char str[MAX_STR_LEN + 1];
    while(n--)
    {
        rand_str(str);
        hash_table_insert(str, n);
    }
    hash_table_print();

    printf("\nlookup testing..........\n");
    HashNode* pNode = hash_table_lookup(key1);
    printf("lookup result:%d\n", pNode->nValue);
    pNode = hash_table_lookup(key2);
    printf("lookup result:%d\n", pNode->nValue);

    printf("\nremove testing..........\n");
    printf("before remove %s:\n", key3);
    hash_table_print();
    hash_table_remove(key3);
    printf("after remove:\n");
    hash_table_print();
    hash_table_release();

    system("pause");
    return 0;
}

运行结果如下:
4

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