自定义数组长度，并求和，可以更改对象值

[c++]代码库

#include<iostream>
using namespace std;
class Data
{
private:
    int data;
public:
    Data()
    {
        data=0;
        cout<<"Data's default constructor."<<endl;
    }
   ~Data()
   {
       cout<<"Data "<<data<<" is erased."<<endl;
   }
   int getValue()
   {
       return data;
   }
   void setValue(int a)
   {
      data=a;
   }
};
class DataArray
{
private:
    int num;
    Data* da;
    public:
    DataArray(int n,int *t)
    {
        num=n;
        da=new Data[n];
        int i;
        for(i=0;i<n;i++)
        {
            da[i].setValue(t[i]);
        }
        cout<<"DataArray's constructor."<<endl;
    }
     int getSum()
     {
         int i,sum=0;
         for(i=0;i<num;i++)
             sum = sum + da[i].getValue();
         return sum;
     }
     ~DataArray()
     {
         delete []da;
         cout<<"DataArray's deconstructor."<<endl;
     }
};
int main()
{
    int i, n;
    Data test, *testP;
    cin>>n;
    int tmp[n];
    for (i = 0; i < n; i++)
        cin>>tmp[i];
    DataArray datas(n, tmp);
    cout<<"Sum is "<<datas.getSum()<<endl;
    testP = new Data;
    cin>>n;
    testP->setValue(n);
    delete testP;
    return 0;
}