del_substr.c

int del_substr(char* str, const char* substr)
{
	while (*str++ != '\0')
	{
		char* s = str;
		const char* c = substr;
		while (*s == *c)
		{
			s++;
			c++;
			if (*c == '\0')
			{
				do
				{
					*str++ = *s++;
				} while (*s != '\0');
				return 1;
			}
		}
	}
	return 0;
}
 
int main (int argc, char const *argv[])
{
	char s[] = "ABCDEFGHIJKLMN";
	char substr[] = "EFG";
	int i = del_substr(s, substr);
	printf("%d : %s\n", i, s);
	return 0;
}