统计输入中关键词出现的次数（二分查找实现）

/* 统计输入的c语言中关键词出现的次数
* @method: 使用二分查找实现，keytab[]关键词必须是按首字母排好序的关键词表
*/

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

struct key
{
char *word;
int count;
} keytab[] = {
"char", 0,
"int", 0,
"void", 0
};

#define MAXWORD 		100
#define NKEYS 	(sizeof keytab / sizeof keytab[0])
int getword(char *, int);
int binsearch(char *, struct key *, int);

main()
{
int n;
char word[MAXWORD];

while(getword(word, MAXWORD) != EOF)
if(isalpha(word[0]))
if((n = binsearch(word, keytab, NKEYS)) >= 0)
keytab
.count++;
for(n = 0; n < NKEYS; n++)
//if(keytab
.count > 0)
printf("%4d %s\n", keytab
.count, keytab
.word);
return 0;
}

/* 根据首字母顺序进行二分查找，tab[]必须是有序的 */
int binsearch(char *word, struct key tab[], int n)
{
int cond;
int low, high, mid;
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;
}

/* 从输入中读取下一个单词*/
int getword(char *word, int lim)
{
int c;
//void ungetch(int);
char *w = word;

while(isspace(c = getchar())) //检查参数c是否为空格字符,即为下一个字母的开始
;
if(c != EOF)
*w++ = c;
if(!isalpha(c)) //判断字符变量c是否为字母
{
*w = '\0';
return c;
}
for(; --lim > 0; w++)
if(!isalnum(*w = getchar())) //判断字符变量c是否为字母或数字
{
//ungetch(*w);
break;
}
*w = '\0';
return word[0];
}