第六週作業

a. 用指針訪問對象
#include<iostream>

using namespace std;
 
class A
{
private:
	int a;
public:
	A() {a=5;}
	A(int aa) : a(aa){}; //定義構造函數，用參數aa初始化數據成員a
    void display()
	{
		cout << a << endl;
	}
};
int main()
 {	
	A *p ;  //定義類A的指針對象p
	p = new A(100);   //用p指向動態對象並初始化爲整數
	p -> display();
	return 0;
}
b. 指針類型作爲成員函數的參數
#include<iostream>

using namespace std;

class A 
{
private:
	int *a; 
	int n; 
	int MaxLen;
 public:
	A(): a(0), n(0), MaxLen(0) {};
	A(int *aa, int nn, int MM);
	~A();
	int GetValue(int i) {return a[i];} 
};
A :: A(int *aa, int nn, int MM)
{
	n = nn;
	MaxLen = MM;
	if(n > MaxLen) exit(1);
	a = new int[MaxLen];
	for(int i = 0; i < MaxLen; ++i)
	*(a+i) = *(aa + i); //以i爲循環變量把aa數組中每個元素值傳送給a數組的對應元素中
}
A :: ~A() //析構函數的類外定義，釋放指針型數據a所指向的空間
{
 	delete [] a;
}

void main()
{
	int b[10] = {1,2,3,4,5,6,7,8,9,10};
	A r(b, 10, 10);
	int i, s = 0;
	for(i = 0; i < 10; ++i) //以i爲循環變量，把r對象的a數據成員中的每個元素值依次累加到s中
	{
		s += r.GetValue(i);
	}
	cout << "s=" << s << endl;
}