char	*strstr(const char *haystack, const char *needle)
{
	char	*h;
	size_t	needle_len;
	size_t	i;
	size_t	j;

	h = (char *)haystack;
	if (!(needle_len = strlen(needle)))
		return (h);
	i = 0;
	while (h[i])
	{
		j = 0;
		while (needle[j] && needle[j] == h[i + j])
			j++;
		if (j == needle_len)
			return (&h[i]);
		i++;
	}
	return (NULL);
}

int		strncmp(const char *s1, const char *s2, size_t n)
{
	if (!n)
		return (0);
	while (*s1 == *s2 && *s1 && --n)
	{
		s1++;
		s2++;
	}
	return ((int)((unsigned char)*s1 - (unsigned char)*s2));
}

char	*strncat(char *restrict s1, const char *restrict s2, size_t n)
{
	size_t	i;
	size_t	len;

	i = 0;
	len = strlen(s1);
	while (s2[i] && i < n)
	{
		s1[len + i] = s2[i];
		i++;
	}
	s1[len + i] = '\0';
	return (s1);
}

char	*strchr(const char *s, int c)
{
	while (*s)
	{
		if (*s == (char)c)
			return ((char *)s);
		s++;
	}
	if (!*s && c == '\0')
		return ((char *)s);
	return (NULL);
}