10. 分离链接散列表

fatal.h

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

#define Error(Str)        FatalError(Str)
#define FatalError(Str)   fprintf(stderr, "%s\n", Str), exit(1)

hashsep.h

/* Interface for separate chaining hash table */
typedef int ElementType;

typedef unsigned int Index;

#ifndef _HashSep_H
#define _HashSep_H

struct ListNode;
typedef struct ListNode *Position;
struct HashTbl;
typedef struct HashTbl *HashTable;

HashTable InitializeTable(int TableSize);
void DestroyTable(HashTable H);
Position Find(ElementType Key, HashTable H);
void Insert(ElementType Key, HashTable H);
ElementType Retrieve(Position P);
void PrintTable(HashTable H);
/* Routines such as Delete are MakeEmpty are omitted */

#endif  /* _HashSep_H */

hashsep.c

#include "fatal.h"
#include "hashsep.h"
#include <stdlib.h>

#define MinTableSize (10)

struct ListNode
{
    ElementType Element;
    Position    Next;
};

typedef Position List;

/* List *TheList will be an array of lists, allocated later */
/* The lists use headers (for simplicity), */
/* though this wastes space */
struct HashTbl
{
    int TableSize;
    List *TheLists;
};

/* Return next prime; assume N >= 10 */
static int NextPrime(int N)
{
    int i;

    if(N % 2 == 0)
        N++;
    for( ; ; N += 2)
    {
        for(i = 3; i * i <= N; i += 2)
            if (N % i == 0)
                break;
        if (i*i > N)
            return N;
    }
}

/* Hash function for ints */
Index Hash(ElementType Key, int TableSize)
{
    return Key % TableSize;
}

HashTable InitializeTable(int TableSize)
{
    HashTable H;
    int i;

    if (TableSize < MinTableSize)
    {
        Error("Table size too small");
        return NULL;
    }

    /* Allocate table */
    H = malloc(sizeof(struct HashTbl));
    if (H == NULL)
        FatalError("Out of space!!!");

      H->TableSize = NextPrime(TableSize);

    /* Allocate array of lists */
    H->TheLists = malloc(sizeof(List) * H->TableSize);
    if (H->TheLists == NULL)
        FatalError("Out of space!!!");

    /* Allocate list headers */
    for (i = 0; i < H->TableSize; i++)
    {
        H->TheLists[i] = malloc(sizeof(struct ListNode));
        if (H->TheLists[i] == NULL)
            FatalError("Out of space!!!");
        else
            H->TheLists[i]->Next = NULL;
    }

    return H;
}

Position Find(ElementType Key, HashTable H)
{
    Position P;
    List L;

    L = H->TheLists[Hash(Key, H->TableSize)];
    P = L->Next;
    while (P != NULL && P->Element != Key)
                        /* Probably need strcmp!! */
        P = P->Next;
    return P;
}

void Insert(ElementType Key, HashTable H)
{
    Position Pos, NewCell;
    List L;

    Pos = Find(Key, H);
    if (Pos == NULL)   /* Key is not found */
    {
        NewCell = malloc(sizeof(struct ListNode));
        if (NewCell == NULL)
            FatalError("Out of space!!!");
        else
        {
            L = H->TheLists[Hash(Key, H->TableSize)];
            NewCell->Next = L->Next;
            NewCell->Element = Key;  /* Probably need strcpy! */
            L->Next = NewCell;
        }
    }
}

ElementType Retrieve(Position P)
{
    return P->Element;
}

void DestroyTable(HashTable H)
{
    int i;

    for(i = 0; i < H->TableSize; i++)
    {
        Position P = H->TheLists[i];
        Position Tmp;

        while(P != NULL)
        {
            Tmp = P->Next;
            free(P);
            P = Tmp;
        }
    }

    free(H->TheLists);
    free(H);
}

void PrintTable(HashTable H)
{
    Position P;
    List L;
    int i;

    for (i = 0; i < H->TableSize; i++)
    {
        L = H->TheLists[i];
        P = L->Next;

        while (P != NULL)
        {
            printf("%d\t", Retrieve(P));
            P = P->Next;
        }
        printf("\n\n");
    }
}

testhash.c

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

#define NumItems 400

int main()
{
    HashTable H;
    Position P;
    int i;
    int j = 0;
    int CurrentSize;

    H = InitializeTable(CurrentSize = 29);

    for (i = 0; i < NumItems; i++, j += 71)
        Insert(j, H);

    PrintTable(H);

    for (i = 0, j = 0; i < NumItems; i++, j += 71)
        if ((P = Find(j, H)) == NULL || Retrieve(P) != j)
            printf("Error at %d\n", j);

    printf("End of program.\n");
    return 0;
}