写一个 c语言 统计关键字

非常好的问题！以下是一个简单的 C 代码，可以统计关键字的数量：

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

#define MAXWORD 100
#define NKEYS (sizeof keytab / sizeof(struct key))

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},
    {"int", 0},
    {"long", 0},
    {"register", 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}
};

int getword(char *, int);
int binsearch(char *, struct key *, int);

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

    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);
        }
    }

    return 0;
}

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];
}

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;
}

int bufp = 0;
char buf[MAXWORD];

int getch(void)
{
    return (bufp > 0) ? buf[--bufp] : getchar();
}

void ungetch(int c)
{
    if (bufp >= MAXWORD) {
        printf("ungetch: too many characters\n");
    } else {
        buf[bufp++] = c;
    }
}

这个程序使用了一个结构体数组 `keytab` 来存储关键字和它们出现的次数。`getword` 函数用来获取输入中的单词，并将其转换为小写形式。`binsearch` 函数用来在 `keytab` 数组中查找单词。最后，程序会输出每个关键字出现的次数。