﻿ C++ Exercises: Display the sum of the specified series - w3resource # C++ Exercises: Display the sum of the specified series

## C++ For Loop: Exercise-23 with Solution

Write a program in C++ to display the sum of the series [ 9 + 99 + 999 + 9999 ...].

Pictorial Presentation: Sample Solution:-

C++ Code :

``````#include <iostream>
using namespace std;

int main()
{
long int n, i, t = 9;
int sum = 0;
cout << "\n\n Display the sum of the series [ 9 + 99 + 999 + 9999 ...]\n";
cout << "-------------------------------------------------------------\n";
cout << " Input number of terms: ";
cin >> n;

for (i = 1; i <= n; i++)
{
sum += t;
cout << t << "  ";
t = t * 10 + 9;
}
cout << "\n The sum of the sarise = " << sum << endl;
}
``````

Sample Output:

``` Display the sum of the series [ 9 + 99 + 999 + 9999 ...]
-------------------------------------------------------------
Input number of terms: 5
9  99  999  9999  99999
The sum of the sarise = 111105
```

Flowchart: C++ Code Editor:

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## C++ Programming: Tips of the Day

What is a smart pointer and when should I use one?

This answer is rather old, and so describes what was 'good' at the time, which was smart pointers provided by the Boost library. Since C++11, the standard library has provided sufficient smart pointers types, and so you should favour the use of std::unique_ptr, std::shared_ptr and std::weak_ptr.

There was also std::auto_ptr. It was very much like a scoped pointer, except that it also had the "special" dangerous ability to be copied - which also unexpectedly transfers ownership.

It was deprecated in C++11 and removed in C++17, so you shouldn't use it.

```std::auto_ptr<MyObject> p1 (new MyObject());
std::auto_ptr<MyObject> p2 = p1; // Copy and transfer ownership.
// p1 gets set to empty!
p2->DoSomething(); // Works.
p1->DoSomething(); // Oh oh. Hopefully raises some NULL pointer exception.
```

Ref : https://bit.ly/3mc9GHE