51.com笔试题
12.6 SJTU
整体来讲，题目出的没水平。
qualify question： 略
选择题：略
大题：
1. 反转链表
#include <iostream>
using namespace std;
struct LNode
{
char data;
LNode * next;
};
LNode * initList()
{
LNode *head=new LNode;
LNode *curPtr, *newPtr;
curPtr=head;
int i=0;
char ch='A';
while(i++<10)
{
newPtr=new LNode;
newPtr->data=ch++;
curPtr->next=newPtr;
curPtr=newPtr;
}
newPtr->next=NULL;
return head;
}
void print(LNode *head)
{
LNode *ptr=head->next;
while(ptr != NULL)
{
cout << ptr->data << " ";
ptr=ptr->next;
}
cout << endl;
}
void reverse(LNode *head)
{
assert(head != NULL && head->next != NULL);
LNode *ptr=head->next->next;
head->next->next=NULL;
while(ptr != NULL)
{
LNode *tmp=ptr->next;
ptr->next=head->next;
head->next=ptr;
ptr=tmp;
}
}
int main()
{
LNode *head=initList();
print(head);
cout << "After reverse: " << endl;
reverse(head);
print(head);
system("PAUSE");
return 0;
}
2. 一个已知递推式的递归程序
3. 数据库查询的问题
主观题：
1. socket网络编程，写一个Helloworld程序，包括client和server两部分
Berkeley Socket API不记得，而且平时很少做网络编程，所以没法写，直接画了个图，说明用到哪几个函数
出这种题很没水平，谁去死记那些API啊，而且这个题叙述都有个地方错了，真是不知道51.com怎么招这种人来出题目考我们，巨faint！
2. 简要介绍leader/follower模式
Design Pattern模式里好像没这个模式吧！
不过提示说和多进程/多线程类似，那我就发挥了，说的和C/S模型下的多线程类似
3. 最后一题考C++的继承和多态的
主要是涉及到基类中protected数据成员和派生类中protected数据成员的重名问题：
#include <iostream>
using namespace std;
class Base
{
protected:
int int_i;
double dbl_x;
public:
Base()
{
int_i=1;
dbl_x=1.5;
}
virtual void foo(int i)
{
cout << "Base::i=" << i << endl;
}
virtual void foo(double x)
{
cout << "Base::x=" << x << endl;
}
virtual void foo()
{
cout << "Base::int_i=" << int_i << endl;
cout << "Base::dbl_x=" << dbl_x << endl;
}
};
class Derived : public Base
{
protected:
int int_i;
public:
Derived()
{
int_i=2;
dbl_x=2.5;
}
virtual void foo(int i)
{
cout << "Derived::i=" << i << endl;
}
virtual void foo()
{
cout << "Derived::int_i=" << int_i << endl;
cout << "Derived::dbl_x=" << dbl_x << endl;
}
};
class Derived2: public Derived
{
protected:
double dbl_x;
public:
Derived2()
{
int_i=3;
dbl_x=3.5;
}
virtual void foo(double x)
{
cout << "Derived2::x=" << x << endl;
}
virtual void foo()
{
cout << "Derived2::int_i=" << int_i << endl;
cout << "Deroved2::dbl_x=" << dbl_x << endl;
}
};
int main()
{
Derived2 d2;
Derived d;
Base b, *p;
p=&d2; p->foo(7); p->foo(7.5); p->foo();
p=&d; p->foo(6); p->foo(6.5); p->foo();
p=&b; p->foo(5); p->foo(5.5); p->foo();
system("PAUSE");
return 0;
}
打印结果：
进一步探讨：
关于这种情况下：到底对象怎样布局呢？？
测试程序如下：
#include <iostream>
using namespace std;
class Base
{
protected:
int int_i;
double dbl_x;
public:
Base()
{
int_i=1;
dbl_x=1.5;
}
virtual void print()
{
cout << "Base::int_i=" << int_i << endl;
cout << "Base::dbl_x=" << dbl_x << endl;
}
};
class Derived : public Base
{
protected:
int int_i;
public:
Derived()
{
int_i=2;
dbl_x=2.5;
}
virtual void print()
{
cout << "Base::int_i=" << Base::int_i << endl;
cout << "Derived::int_i=" << int_i << endl;
cout << "Base::dbl_x=" << Base::dbl_x << endl;
cout << "Derived::dbl_x=" << dbl_x << endl;
}
};
class Derived2: public Derived
{
protected:
double dbl_x;
public:
Derived2()
{
int_i=3;
dbl_x=3.5;
}
virtual void print()
{
cout << "Base::int_i=" << Base::int_i << endl;
cout << "Derived::int_i=" << Derived::int_i << endl;
cout << "Derived2::int_i=" << int_i << endl;
cout << "Base::dbl_x=" << Base::dbl_x << endl;
cout << "Derived::dbl_x=" << Derived::dbl_x << endl;
cout << "Derived2::dbl_x=" << dbl_x << endl;
}
};
int main()
{
Derived2 d2;
Derived d;
Base b, *p;
p=&d2;
p->print();
p=&d;
p->print();
p=&b;
p->print();
system("PAUSE");
return 0;
}
很显然的看到，派生类中的重名成员只不过隐藏(hide)了基类的同名成员，默认情况下是访问派生类中的成员，要访问基类中同名成员必须加上类域符(::)
既然是隐藏，那么在基类子对象中仍然是存在的！要记住，无论怎样继承，C++都需要保证基类子对象的完整性！
这和成员函数同名一样，只不过成员函数同名时要分清hide和override！
