第四章 堆与拷贝构造函数
一 、程序阅读题
1、给出下面程序输出结果。
#include <iostream.h>
class example
{int a;
public:
example(int b=5){a=b++;}
void print(){a=a+1;cout <<a<<"";}
void print()const
{cout<<a<<endl;}
};
void main()
{example x;
const example y(2);
x.print();
y.print();
}
答：6 2
2、运行程序，写出程序执行的结果。
#include<iostream.h>
class Location
{ public:
int X,Y;
void init(int initX,int initY);
int GetX();
int GetY();
};
void Location::init (int initX,int initY)
{X=initX;
Y=initY;
}
int Location::GetX()
{return X;
}
int Location::GetY()
{return Y;
}
void display(Location& rL)
{cout<<rL.GetX()<<" "<<rL.GetY()<<'＼n';
}
void main()
{
Location A［5］={{5,5},{3,3},{1,1},{2,2},{4,4}};
Location *rA=A;
A［3］.init(7,3);
rA->init(7,8);
for (int i=0;i<5;i++)
display(*(rA++));
}
答：
7 8
3 3
1 1
7 3
4 4
3. 给出下面程序输出结果。
#include <iostream.h>
int a[8］={1,2,3,4,5,6,7};
void fun(int *pa,int n);
void main()
{int m=8;
fun(a,m);
cout<<a［7］<<endl;
}
void fun(int *pa,int n)
{for (int i=0;i<n-1;i++)
*(pa+7)+=*(pa+i);
}
答：28
4. 给出下面程序输出结果。
#include <iostream.h>
class A
{
int *a;
public:
A(int x=0):a(new int(x)){}
~A() {delete a;}
int getA() {return *a;}
void setA(int x) {*a=x;}
};
void main()
{
A x1,x2(3);
A *p=&x2;
(*p).setA(x2.getA()+5);
x1.setA(10+x1.getA());
cout<<x1.getA()<<""<<x2.getA()<<endl;
}
答：10 8
5. 阅读下面的程序，写出运行结果：
#include < iostream.>
using namespace std;
class Samp
{
public:
void Set_i_j(int a, int b){i=a,j=b;}
~Samp()
{
cout <<"Destroying.." << i <<endl;
}
int GetMulti () { return i * j; }
protected:
int i;
int j;
};
int main ()
{
Samp * p;
p = new Samp[l0];
if(!p)
{
cout << "Allocation error \ n";
return;
}
for(int j =0; j<l0; j ++)
p[j]. Set_i_j (j, j);
for(int k=0; k<l0; k++)
cout <<"Multi[" <<k <<"] is:"<< p[k].GetMulti () <<endl;
delete [ ] p;
return 0;
}
答：
Multi[0] is:0
Multi[1] is:1
Multi[2] is:4
Multi[3] is:9
Multi[4] is:16
Multi[5] is:25
Multi[6] is:36
Multi[7] is:49
Multi[8] is:64
Multi[9] is:81
Destroying..9
Destroying..8
Destroying..7
Destroying..6
Destroying..5
Destroying..4
Destroying..3
Destroying..2
Destroying..1
Destroying..0
6. 写出下面程序的运行结果，请用增加拷贝构造函数的方法避免存在的问题。
#include < iostream>
using namespace std;
class Vector
{
public:
Vector (int s = 100);
int& Elem(int ndx);
void Display();
void Set ();
~Vector ();
protected:
int size;
int* buffer;
}
Vector::Vector (int s)
{
buffer = new int [size = s];
for(int i = O; i<size; i + + )
buffer [i] = i* i;
}
int& Vector:: Elem(int ndx)
{
if(ndx< 0 || ndx> = size)
{
cout << "error in index" <<endl;
exit (1);
}
return buffer [ndx];
}
void Vector::Display ()
{
for(int j =0; j< size; j ++)
cout << buffer[j] <<endl;
}
void Vector:: Set ()
{
for(int j =0; j<size; j++)
buffer[j] = j + 1;
}
Vector:: ~ Vector()
{
delete [] buffer;
}
int main()
{
Vector a(10);
Vector b(a);
a. Set ();
b. Display ();
return 0;
}
答：
1
1
4
9
16
25
36
49
64
81
7.读下面的程序与运行结果，添上一个拷贝构造函数来完善整个程序。
#include < iostream>
using namespace std;
class CAT
{
public:
CAT();
CAT(const CAT&);
~CAT();
int GetAge() const (return * itsAge;)
void SetAge(int age) { * itsAge = age; }
protected:
int * itsAge;
};
CAT::CAT ()
{
itsAge = new int;
*itsAge = 5;
}
CAT::~CAT ()
{
delete itsAge;
itsAge = 0;
}
void main()
{
CAT frisky;
cout << "frisky's age:" << frisky. GetAge() <<endl;
cout <<"Setting frisky to 6... \ n";
frisky. SetAge ( 6 );
cout << "Creating boots from frisky \ n";
CAT boots(frisky);
cout <<"frisky's age:" << frisky. GetAge() <<endl;
cout << "boots'age:" << boons. GetAge () <<endl;
cout << "setting frisk,, to 7 .... n";
frisky. SetAge (7);
cout <<"frisky"s age:" << frisky. GetAge() <<endl;
cout <<"boots' age:" << boots. GetAge() <<endl;
}
答：
frisky's age:5
Setting frisky to 6...
Creating boots from frisky
frisky's age:6
boots' age:6
Setting frisky to 7...
frisky's age:7
boots' age:6
添加
CAT::CAT(const CAT& other) {
itsAge = new int;
*itsAge = *other.itsAge;
}
CAT::~CAT() {
delete itsAge;
itsAge = 0;
}
