﻿ C++ : Show the first 15 Narcissistic decimal numbers

# C++ Exercises: Generate and show the first 15 Narcissistic decimal numbers

## C++ Numbers: Exercise-13 with Solution

Write a program in C++ to generate and show the first 15 Narcissistic decimal numbers.

Pictorial Presentation:

Sample Solution:

C++ Code :

``````#include <iostream>
#include <cmath>
using namespace std;
int main()
{
cout << "\n\n Find the first 15 Narcissistic decimal numbers: \n";
cout << " -----------------------------------------------------\n";
cout << " The first 15 Narcissistic decimal numbers are: \n";
int i,ctr,j,orn,n,m,sum;
orn=1;
for (i=1;i<=15;)
{
ctr=0;
sum=0;
n=orn;
while(n>0)
{
n=n/10;
ctr++;
}
n=orn;
while(n>0)
{
m=n % 10;
sum=sum+pow(m,ctr);
n=n/10;
}
if(sum==orn)
{
cout<<orn<<" ";
i++;
}
orn++;
}
cout<<endl;
}
``````

Sample Output:

```Find the first 15 narcissistic decimal numbers:
-----------------------------------------------------
The first 15 narcissistic decimal numbers are:
1 2 3 4 5 6 7 8 9 153 370 371 407 1634 8208
```

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