面试题八股文之算法题

实现memcpy函数

#include 
using namespace std;
 
void *Memcpy(void *dst, const void *src, size_t size)
{
    char *psrc;
    char *pdst;
 
    if(NULL == dst || NULL == src)
    {
        return NULL;
    }
 
    if((src < dst) && (char *)src + size > (char *)dst) // 自后向前拷贝
    {
        psrc = (char *)src + size - 1;
        pdst = (char *)dst + size - 1;
        while(size--)
        {
            *pdst-- = *psrc--;
        }
    }
    else
    {
        psrc = (char *)src;
        pdst = (char *)dst;
        while(size--)
        {
            *pdst++ = *psrc++;
        }
    }
 
    return dst;
}

int main(int argc, char *argv[])
{
    char buf[100] = "abcdefghijk";
    //memcpy(buf+2, buf, 5);
    Memcpy(buf+2, buf, 5);
    printf("%sn", buf+2);
}

循环引用

#include 

using namespace std;

class B;
class A {
public:
    shared_ptr pointer_B;
    ~A() {
        std::cout << "A已经被删除" << std::endl;
    }
};

class B {
public:
    shared_ptr pointer_A;// 将shared_ptr修改为weak_ptr
    ~B() {
        std::cout << "B已经被删除" << std::endl;
    }

};

int main()
{
    {
        std::shared_ptr pointer_A(new A);
        std::shared_ptr pointer_B(new B);
        pointer_A->pointer_B = pointer_B;
        pointer_B->pointer_A = pointer_A;
    }

    return 0;
}

#include 
#include 
#include 
#include 

using namespace std;

int data = 1;
mutex mt1,mt2;

void a2() {
	mt2.lock();
	sleep(1);
	data = data * data;
	mt1.lock();  //此时a1已经对mt1上锁，所以要等待
	cout<
	mt1.lock();
	sleep(1);
	data = data+1;
	mt2.lock();  //此时a2已经对mt2上锁，所以要等待
	cout<
	thread t2(a2);
	thread t1(a1);
	
	t1.join();
	t2.join();
	cout<<"main here"<