C语言实现strstr()函数：返回字符串中首次出现子串的地址

#include 
#include 

const char* mmy_strstr(const char* str1, const char* str2) {
	assert(str1 != NULL);
	assert(str2 != NULL);
	assert(*str1 != '');
	assert(*str2 != '');

	const char* black = str1;

	while (*black != '') {
		const char* red = black;
		const char* sub = str2;
		while (*red != '' && *sub != '' && *red == *sub) {
			red++;
			sub++;
		}
		if (*sub == '') {
			return black;
		}
		black++;
	}
	return NULL;
}

int main() {

	char str1[1024] = "hello llo llo";
	char str2[1024] = "llo";

	printf("%c", *mmy_strstr(str1, str2));
	return 0;
}

实现结果：