﻿ C++ Exercises: Find Strong Numbers within a range of numbers - w3resource

# C++ Exercises: Find Strong Numbers within a range of numbers

## C++ Numbers: Exercise-46 with Solution

Write a program in C++ to find Strong Numbers within a range of numbers.

Sample Solution:

C++ Code:

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

int main()
{
int i, n, n1, s1 = 0, j, k, en, sn;
long fact;
cout << "\n\n Find Strong Numbers within an range of numbers:\n";
cout << "----------------------------------------------------\n";
cout << " Input starting range of number: ";
cin >> sn;
cout << " Input ending range of number: ";
cin >> en;
cout << " The Strong numbers are: ";
for (k = sn; k <= en; k++)
{
n1 = k;
s1 = 0;
for (j = k; j > 0; j = j / 10)
{
fact = 1;
for (i = 1; i <= j % 10; i++)
{
fact = fact * i;
}
s1 = s1 + fact;
}
if (s1 == n1)
cout << n1 << "  ";
}
cout << endl;
}
``````

Sample Output:

```Check whether a number is Strong Number or not:
-------------------------------------------------------
Input starting range of number: 1
Input ending range of number: 500
The Strong numbers are: 1  2  145
```

Flowchart:

C++ Code Editor:

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## C++ Programming: Tips of the Day

How to use the PI constant in C++?

On some (especially older) platforms (see the comments below) you might need to

#define _USE_MATH_DEFINES and then include the necessary header file:
`#include<math.h>`

and the value of pi can be accessed via:

`M_PI`

In math.h (2014) it is defined as:

`# define M_PI           3.14159265358979323846  /* pi */`

but check your math.h for more. An extract from the "old" math.h (in 2009):

```/* Define _USE_MATH_DEFINES before including math.h to expose these macro
* definitions for common math constants.  These are placed under an #ifdef
* since these commonly-defined names are not part of the C/C++ standards.
*/```

However:

1. on newer platforms (at least on my 64 bit Ubuntu 14.04) I do not need to define the _USE_MATH_DEFINES
2. On (recent) Linux platforms there are long double values too provided as a GNU Extension:
`# define M_PIl          3.14159265358979323846`

Ref: https://bit.ly/3G4BgzQ