哈希表分离链接法--两种初始化方法及其对比

来源：互联网发布：mac rebel和diva对比编辑：程序博客网时间：2024/05/17 22:52

在教材中多为第一种方法。实际上可以改变，减少h->tablesize次的malloc()操作

下面是依次是声明、方法一、方法二：

typedef int ElementType;/* hashSep.h */#ifndef HashSep_H#define HashSep_Htypedef unsigned int Index;//Hash()散列函数的返回类型struct listnode;typedef struct listnode *position;typedef struct listnode *list;struct hashta1;typedef struct hashta1 *hashtable;list MakeEmpty(void);hashtable InitTable_1(int tableSize);//一个不太好的初始化程序hashtable InitTable_2(int tableSize);//一个比较好的初始化程序void DestoryTable(hashtable h);position Find(ElementType key, hashtable h);void Insert(ElementType key, hashtable h);ElementType Retrieve(position p);#endif/* ENDING *//* hashSep.c *//* The list using headers */#include<stdio.h>#include<stdlib.h>#define MinTableSize (5)struct listnode{ElementType element;position next;};struct hashta1{int  tableSize;list *theLists;//指向指针的指针};

hashtable InitTable_1(int tableSize){hashtable h;int i;if (tableSize < MinTableSize){printf("Table size too small!!\n");return NULL;}/* allocate tabel */h = malloc(sizeof(struct hashta1));if (h == NULL){printf("Out of space!!\n");exit(1);}h->tableSize =NextPrime(tableSize);/* allocate array of lists */h->theLists = malloc(sizeof(list)*h->tableSize);   //本方法中，存放的是多个headers指针，不是listnode结构体，故下面要有 h->tableSize次调用malloc函数为数组中的每个指针赋值if(h->theLists==NULL){ printf("Out of space!!\n");exit(1);}/* allocate list header */for (i = 0;i < h->tableSize;++i){h->theLists[i] = malloc(sizeof(struct listnode));if (h->theLists[i] == NULL){printf("Out of space!!\n");exit(1);}elseh->theLists[i]->next= NULL;}return h;}
hashtable InitTable_2(int tableSize){hashtable h;int i;if (tableSize < MinTableSize){printf("Table size too small!\n");return NULL;}/* allocate table */h = malloc(sizeof(struct hashta1));if (h == NULL){printf("Out of space!!\n");exit(1);}h->tableSize = NextPrime(tableSize);/* allocate array of list */h->theLists = malloc(sizeof(struct listnode)*h->tableSize);   //避免了调用h->tableSize次的malloc()为h->theLists[i]赋值,降低时间复杂度if (h->theLists == NULL){printf("Out of space!!\n");exit(1);}/* allocate list header */for (i = 0;i < h->tableSize;++i){h->theLists[i]->next= MakeEmpty();}}

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