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C++ Exercises: Find the Armstrong number for a given range of number

C++ Numbers: Exercise-44 with Solution

Write a program in C++ to find the Armstrong number for a given range of number.

/*When the sum of the cube of the individual digits of a number
is equal to that number, the number is called Armstrong number. For example 153.
Sum of its divisor is 13 + 53;+ 33; = 1+125+27 = 153*/

Sample Solution:

C++ Code:

#include <iostream>
#include <math.h>
using namespace std;

int main()
{
    int num, r, sum, t, mm;
    int sno, eno;
    cout << "\n\n Find the Armstrong number for a given range of number:\n";
    cout << "-----------------------------------------------------------\n";
    cout << " Input starting number of range: ";
    cin >> sno;
    cout << " Input ending number of range: ";
    cin >> eno;
    cout << " Armstrong numbers in given range are: " << endl;
    for (num = sno; num <= eno; num++) 
    {
        t = num;
        sum = 0;
        while (t != 0) 
        {
            r = t % 10;
            mm = pow(r, 3);
            sum = sum + mm;
            t = t / 10;
        }
        if (sum == num)
            cout << num << " ";
    }
    cout << endl;
}

Sample Output:

 Find the Armstrong number for a given range of number:                
-----------------------------------------------------------            
 Input starting number of range: 25                                    
 Input ending number of range: 200                                     
 Armstrong numbers in given range are:                                 
153

Flowchart:

Flowchart: Find the Armstrong number for a given range of number

C++ Code Editor:

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Previous: Write a C++ program to check whether a given number is an Armstrong number or not.
Next: Write a program in C++ to check whether a number is a Strong Number or not.

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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