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();
}
6 3
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++));
}
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);
}
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;
}
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; } |
| 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 |
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; } 拷贝构造函数： Vector::Vector(const Vector& other){ size = other.size; buffer = new int[size]; for(int i=0;i<size;i++) buffer[i] = other.buffer[i]; } 结果： 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; } |
拷贝构造函数：
CAT::CAT(const CAT& other) {
itsAge = new int;
*itsAge = *other.itsAge;
}
运行结果为：
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
)
