编写支持对其分配的malloc和free函数，分配内存时，malloc函数返回的地址必须能被2的n次方整除

//required_bytes为需要新建的字节数，alignment为首位置需要整除的数值
//按照题目要求，alignment应该是2的n次方
void* aligned_malloc(size_t required_bytes, size_t alignment)
{
	size_t offset = alignment - 1 + sizeof(void*);
	void* p = (void*)malloc(required_bytes+offset);
	if (p == nullptr)
		return nullptr;
	void* res = (void*)(((size_t)(p)+offset)&~(alignment-1));//关键
	void** tmp = (void**)res;
	tmp[-1] = p;	
	return res;
}

void aligned_free(void* r)
{
	if (r != nullptr)
	{
		void** tmp = (void**)r;
		free(tmp[-1]);
		r = nullptr;
	}
	
}