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【C】 K&C书中统计关键字出现次数

作者:古爵士 / 发布于2012/10/8/ 619

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h></div>
<div>define NKEYS ( sizeof keytab / sizeof keytab[0] )
#define MAXWORD 100</div>
<div>struct key {
 char *word;
 int count;
} keytab[] = {
 "auto", 0,
 "break", 0,
 "case", 0,
 "char", 0,
 "const", 0,
 "continue", 0,
 "default", 0,
 "do", 0,
 "double", 0,
 "else", 0,
 "enum", 0,
 "extern", 0,
 "float", 0,
 "for", 0,
 "goto", 0,
 "if", 0,
 "inline", 0,
 "int", 0,
 "long", 0,
 "register", 0,
 "restrict", 0,
 "return", 0,
 "short", 0,
 "signed", 0,
 "sizeof", 0,
 "static", 0,
 "struct", 0,
 "switch", 0,
 "typedef", 0,
 "union", 0,
 "unsigned", 0,
 "void", 0,
 "volatile", 0,
 "while", 0,
 "_Bool", 0,
 "_Complex", 0,
 "_Imaginary", 0,
 "_Generic", 0
};</div>
<div>int getword(char *, int);
int binsearch(char *, struct key *, int);</div>
<div>/* 统计输入中C语言关键字的出现次数 */
int main(void)
{
 int n;
 char word[MAXWORD];</div>
<div> while (getword(word,MAXWORD) != EOF)
 if ( isalpha(word[0]) )
 if ( (n = binsearch(word, keytab, NKEYS)) >= 0 )
keytab[n].count++;
 
 for (n = 0; n < NKEYS; n++)
 if (keytab[n].count > 0)
 printf("%4d %s\n", keytab[n].count, keytab[n].word);</div>
<div> return EXIT_SUCCESS;
}
<div>/* 在tab[o]到tab[n-1]中查找单词 */
int binsearch(char *word, struct key tab[], int n)
{
 int cond;
 int low, high, mid;</div>
<div> low = 0;
 high = n - 1;
 while( low <= high )
 {
 mid = ( low + high) / 2;
 if ( (cond = strcmp(word, tab[mid].word)) < 0 )
high = mid - 1;
 else if (cond > 0)
low = mid + 1;
 else
return mid;
 }
 return -1;
}
</div>

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