好程序員訓練營
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------我的c語言筆記，期待與您交流!
#include<stdio.h>
#include<string.h>
#include<ctype.h>
#define MAXWORD 100
#define BUFSIZE 100
#define NKEYS (sizeof keytab/sizeof keytab[0])
char buf[BUFSIZE];
int bufp=0;
struct key
{
char *word;
int count;
}keytab[]={
{"auto",0},{"break",0},{"case",0},{"char",0},{"const",0},{"continue",0},{"default",0},/* ...*/ ，{"unsigned",0},{"void",0},{"volatile",0},{"while",0}
};
struct key
{
char *word;
int count;
}tab;
int getword(char *,int);
struct key *binsearch(char *,struct key *,int);
/*取回一個字符（可能是壓回的字符)*/
int getch(void)
{
return (bufp>0) ? buf[--bufp]:getchar();
}
/*把字符壓回到輸入中*/
void ungetch(int c)
{
if(bufp >= BUFSIZE)
printf("ungetch: too many characters\n");
else
buf[bufp++]=c;
}
/*getword函數：從輸入中讀取下一個單詞或字符*/
int getword(char *word,int lim)
{
int c,getch(void);
void ungetch(int);
char *w=word;
while(isspace(c=getch()));
if(c!=EOF)
*w++=c;
if(!isalpha(c))
{
*w='\0';
return c;
}
for(;--lim>0;w++)
if(!isalnum(*w=getch()))
{
ungetch(*w);
break;
}
*w='\0';
return word[0];
}
/*binsearch函數：在tab[0]到tab[n-1]中查找單詞(折半查找函數)*/
struct key *binsearch(char *word,struct key *tab,int n)
{
int cond;
struct key *low=&tab[0];
struct key *high=&tab[n];
struct key *mid;
while(low<high)
{
mid=low+(high-low)/2;
if((cond=strcmp(word,mid->word))<0)
high=mid;
else if(cond>0)
low=mid+1;
else
return mid;
}
return NULL;
}
/*統計關鍵字出現的次數：採用指針方式實現的版本*/
int main()
{
char word[MAXWORD];
struct key *p;
while(getword(word,MAXWORD)!=EOF)
if(isalpha(word[0]))
if((p=binsearch(word,keytab,NKEYS))!=NULL)
p->count++;
for(p=keytab;p<keytab+NKEYS;p++)
if(p->count>0)
printf("%4d %s\n",p->count,p->word);
return 0;
}