transform string

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static char t(char);
static char t(char c) {
    static const char *tab[] = { "aehiouwy", "bfpv", "cgjkqsxz", "dt", "l", "mn", "r" };
    if (!islower(c)) {
        return c;
    }
    for (size_t i = 0; i < sizeof tab / sizeof tab[0]; ++i) {
        if (strchr(tab[i], c)) {
            return '0' + i;
        }
    }
    // NOTREACHED
    return '\0';
}
int main(void) {
    char buf[BUFSIZ];
    if(!fgets(buf, BUFSIZ, stdin)) {
        goto end;
    }
    int len = strlen(buf);
    if (buf[len - 1] == '\n') {
        buf[len - 1] = '\0';
        --len;
    }
    if (len < 1) {
        goto end;
    }
    for (int i = 0; i < len; ++i) {
        if (!isalpha(buf[i])) {
            goto end;
        }
    }
    char *p = buf;
    char *prev = NULL;
    do {
        if (strchr("aeiouy", *p)) {
            prev = p;
            continue;
        }
        if (strchr("hw", *p)) {
            continue;
        }
        if (!prev || t(*prev) != t(*p)) {
            printf("%c", t(*p));
        }
        prev = p;
    } while (*++p);
    puts("");
    exit(0);
end:
    exit(1);
}