int main()
{
	if (strlen("abc") - strlen("abcdef"))
		printf("hehe");
	else
		printf("haha");
	return 0;
}

size_t my_strlen(const char* a)
{
	assert(a);
	int count = 0;
	while (*a)
	{
		count++;
		a++;
	}
	return count;
}

int main()
{
	char arr1[] = "xxxxxxxxxxxxxxx";
	//char *p = "xxx";//不可变且空间小
	char arr2[] = "abcd\0efg";
	strcpy(arr1, arr2);
	printf("%s", arr1);
	return 0;
}

int main()
{
	char a[] = "abcde";
	char b[] = "abc";
	strncpy(a, b, 6);
	printf("%s", a);
	return 0;
}

char* my_strcpy(char* a1, const char* a2)//原指针被修改，不加const
{
	assert(a1 && a2);
	char* ret = a1;
	while (*a1++ = *a2++)
	{
		;
	}
	return ret;
}

char* my_strcat(char* a, const char* b)
{
	assert(a && b);
	char* p = a;
	//先找到a字符串为'\0'的位置
	while (*a)
	{
		a++;
	}
	while (*a++ = *b++)
	{
		;
	}
	return p;
}

int my_strcmp(const char* a, const char* b)
{
	assert(a && b);
	while (*a == *b)
	{
		if (*b == '\0')
			return 0;
		a++;
		b++;
	}
	
	return *a - *b;//这样一步到位
}

int main()
{
	char a[] = "I am a student.";
	char b[] = "am";
	printf("%s", strstr(a, b));
	return 0;
}

char* my_strstr(const char* str1, const char* str2)
{
	assert(str1 && str2);
	char* s1;
	char* s2;
	char* cp = str1;
	if (*str2 == '\0')//如果传入了""
		return str1;
	while (*cp)
	{
		s1 = cp;
		s2 = str2;
		while (*s1 == *s2 && *s1 && *s2)
		{
			s1++;
			s2++;
		}
		if (*s2 == '\0')
		{
			return cp;
		}
		cp++;
	}
	return NULL;
}

int main()
{
	char a[] = "123@qq.com";
	char b[] = "@.";
	printf("%s\n", strtok(a, b));//分割了123
	printf("%s\n", strtok(NULL, b));//分割了qq
	printf("%s\n", strtok(NULL, b));//分割了com
	return 0;
}

int main()
{
    char *p = "666@qq.com";
    const char* sep = ".@";
    char arr[30];
    char *str = NULL;
    strcpy(arr, p);//将数据拷贝一份，处理arr数组的内容
    for(str=strtok(arr, sep); str != NULL; str=strtok(NULL, sep))
    {
        printf("%s\n", str);
    }
}