参考网址：https://www.codewars.com/kata/5266876b8f4bf2da9b000362/solutions/c

（1）使用asprintf，asprintf()可以说是一个增强版的sprintf()

（2）在不确定字符串的长度时，能够根据格式化的字符串长度，申请足够的内存空间。

char* likes(size_t n, const char *const names[n]) {
  char *buf;
  switch (n) {
    case 0:  { asprintf(&buf, "no one likes this"); break; }
    case 1:  { asprintf(&buf, "%s likes this", names[0]); break; }
    case 2:  { asprintf(&buf, "%s and %s like this", names[0], names[1]); break; }
    case 3:  { asprintf(&buf, "%s, %s and %s like this", names[0], names[1], names[2]); break; }
    default: { asprintf(&buf, "%s, %s and %d others like this", names[0], names[1], n-2); break; }
  }
  return buf;
}

（3）使用sprintf

char* likes(size_t n, const char *const names[n]) {

    char * ret, * count_as_str;
    switch(n) {
        case 0:
            return strdup("no one likes this");
        case 1:
            ret = calloc(12 + strlen(names[0]), sizeof(char));
            sprintf(ret, "%s likes this", names[0]);
            return ret;
        case 2:
            ret = calloc(16 + strlen(names[0]) + strlen(names[1]), sizeof(char));
            sprintf(ret, "%s and %s like this", names[0], names[1]);
            return ret;
        case 3:
            ret = calloc(18 + strlen(names[0]) + strlen(names[1]) + strlen(names[2]), sizeof(char));
            sprintf(ret, "%s, %s and %s like this", names[0], names[1], names[2]);
            return ret;
        default:
            asprintf(&count_as_str, "%d", n-2);
            ret = calloc(25 + strlen(names[0]) + strlen(names[1]) + strlen(count_as_str), sizeof(char));
            sprintf(ret, "%s, %s and %s others like this", names[0], names[1], count_as_str);
            return ret;
    }
}