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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:

Flowchart: Find Strong Numbers within a range of numbers

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