分离链接散列表C语言实现实例

/* hash_sep.h */

#ifndef _HASH_SEP_H
#define _HASH_SEP_H

#define MIN_TABLE_SIZE    5
struct list_node;
typedef struct list_node *position;
struct hash_tbl;
typedef struct hash_tbl *hash_table;
typedef unsigned int hash_index;

hash_index hash(const char *key, int table_size);
hash_table initialize_table(int table_size);
void destroy_table(hash_table h);
position find(char *key, hash_table h);
void insert(char *key, hash_table h);
char *retrieve(position p);

#endif

/* hash_sep.c */

#include "hash_sep.h"
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <error.h>

struct list_node
{
    char element[100];
    position next;
};

typedef position list;

/* List *the_lists will be an array of lists, allocated later */
/* the lists use headers (for simplicity), */
/* though this wastes space */
struct hash_tbl
{
    int table_size;
    list *the_lists;
};


hash_index
hash(const char *key, int table_size)
{
    unsigned int hash_val = 0;
    
    while(*key != '')
        hash_val = (hash_val << 5) + *key++;

    return hash_val % table_size;
}

hash_table
initialize_table(int table_size)
{
    hash_table h;
    int i;
    
    if(table_size < MIN_TABLE_SIZE)
    {
        printf("Table size too small");
        return NULL;
    }

    /* allocate table */
    h = malloc(sizeof(struct hash_tbl));
    if(h == NULL)
    {
        perror("malloc");
        exit(1);
    }
    
    h->table_size = table_size;

    /* allocate array of lists */
    h->the_lists = malloc(sizeof(list) * h->table_size);
    if(h->the_lists == NULL)
    {
        perror("malloc");
        exit(1);
    }
    
    /* allocate list headers */
    for(i = 0; i < h->table_size; i++)
    {
        h->the_lists[i] = malloc(sizeof(struct list_node));
        if(h->the_lists[i] == NULL)
        {
            perror("malloc");
            exit(1);
        }
        else
            h->the_lists[i]->next = NULL;
    }

    return h;
}

position
find(char *key, hash_table h)
{    
    
    position p;
    list l;
    
    l = h->the_lists[hash(key, h->table_size)];
    p = l->next;

    while(p != NULL && strcmp(p->element, key))
        p = p->next;

    return p;
}

void 
insert(char *key, hash_table h)
{
    position pos;
    position new_cell;
    list l;
    
    pos = find(key, h);
    if(pos == NULL)
    {
        new_cell = malloc(sizeof(struct list_node));
        if(new_cell == NULL)
        {
            perror("malloc");
            exit(1);
        }
        else
        {
            l = h->the_lists[hash(key, h->table_size)];
            new_cell->next = l->next;
            strcpy(new_cell->element, key);
            l->next = new_cell;
        }
    }
}

void 
destroy_table(hash_table h)
{
    int i;

    if(h != NULL)
    {
        for(i = 0; i < h->table_size; i++)
            free(h->the_lists[i]);
        free(h->the_lists);
        free(h);        
    }
}

char * 
retrieve(position p)
{
    return p->element;
}

/* hash_test.c */

#include <stdio.h>
#include "hash_sep.h"

int
main(void)
{
    position p1;
    position p2;
    position p3;
    char *tmp1;
    char *tmp2;
    char *tmp3;
    char array1[] = "zhu";
    char array2[] = "yong";
    char array3[] = "chang";    
    hash_table htp;
    
    htp = initialize_table(10);

    insert(array1, htp);
    insert(array2, htp);
    insert(array3, htp);
    p1 = find("zhu", htp);
    p2 = find("yong", htp);
    p3 = find("chang", htp);
    tmp1 = retrieve(p1);
    tmp2 = retrieve(p2);
    tmp3 = retrieve(p3);

    printf("
%s %s %s

", tmp1, tmp2, tmp3);
    
    destroy_table(htp);
}

实例测试结果: