哈希表模拟#define

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代码：

#include <stdio.h>#include <string.h>#include <stdlib.h>struct nlist//表的节点{    struct nlist *next;    char *name;    char *dfen;};#define HASHSIZE 101static struct nlist *hashtab[HASHSIZE] = {NULL};unsigned shash(char *);//算哈希值struct nlist *lookup(struct nlist *);//找节点struct nlist *install(char *, char *);//加节点int main(){}unsigned shash(char *s){    unsigned hashval;    for(hashval = 0; *s != '\0'; s++)//计算哈希值，为啥是31。。大概是统计学什么什么的        hashval = *s + 31 * hashval;    return hashval % HASHSIZE;}struct nlist *lookup( char * name ){    struct nlist *np;    for( np = hashtab[shash(name)]; np != NULL; np = np->next )//通过哈希值查表        if( strcmp(name, p->name) == 0)            return p;    return NULL;}struct nlist *install(char *name, char *dfen){    struct nlist *np;    if( (np = lookup(name)) == NULL)//如果name不存在    {        np = (struct nlist*)malloc( sizeof(*np));        if(np == NULL || (np->name = strdup( name )) == NULL)//注意main里最后free            return NULL;        hashval = shash(name);        np->next = hashtab[hashval];    }    else//如果存在就删了先前define的内容        //strcpy(np->dfen, dfen);        free( (void*)np->defn );    if( (np = strdup(dfen) ) == NULL)        return NULL;    return np;}

懒得没写main调用。。。

来自《C程序设计语言》

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