题目：

 给出的头文件：

#include <iostream>
#include "array.h"
using namespace std;

int main()
{
	Array a1;
	int n;
	cin >> n;
	for (int i = 0;i != n; ++i) {
		int t;
		cin >> t;
		a1.Push_back(t);
	}

	Array a2(a1);
	cout << "\nThere're " << a2.length() << " numbers:" << endl;
	a2.Print();
	a2.Push_back(10);
	cout << "\nAfter push_back,";
	cout << "there're " << a2.length() << " numbers:" << endl;
	a2.Print();

	Array a3;
	a3.Print();
	a3 = a1;
	cout << "After operator=,";
	cout << "there're " << a3.length() << " numbers:" << endl;
	a3.Print();
}

 考点：

动态空间分配

法一：new

array.h

/**********Program**********/

class Array
{
    private:
    int size;
    int *ptr;
    public:
    Array();
    Array(const Array& a);
    ~Array();

    void Push_back(int v);
    Array& operator=(const Array& a);
    int length();
    void Print();
};

/**********  End  **********/ 

array.cpp

/**********Program**********/
#include"array.h"
#include <iostream>
using namespace std;

Array::Array(const Array& a)
{
    if(a.size>0){
        size=a.size;
        ptr=new int[size];
       for(int i=0;i<size;i++)
       ptr[i]=a.ptr[i];
    }
}
Array::Array()
{
    size=0;
    ptr=new int[size];
}

Array::~Array(){
    delete []ptr;
    ptr=NULL;
}

Array& Array::operator=(const Array& a)
{
    delete []ptr;
    if(a.size>0){
        size=a.size;
        ptr=new int[size];
        for(int i=0;i<size;i++){
            ptr[i]=a.ptr[i];
        }
    }
    else ptr=NULL;
}

void Array::Print()
{
    if(size!=0){
        for(int i=0;i<size;i++){
            cout<<ptr[i];
            if(i!=size-1)cout<<" ";
        }
        cout<<"\n";
    }
    else
    cout<<"\nIt's empty!\n";
}
void Array::Push_back(int v)
{
    int *temp=new int[size+1];
    for(int i=0;i<size;i++)temp[i]=ptr[i];
    temp[size]=v;
    delete []ptr;
    ptr=temp;
    size++;
}
int Array::length()
{
    return size;
}

/**********  End  **********/