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C++ Exercises: Display the first 10 Lucus numbers

C++ Numbers: Exercise-14 with Solution

Write a program in C++ to display the first 10 Lucus numbers.

Pictorial Presentation:

C++ Exercises: Display the first 10 Lucus numbers

Sample Solution:

C++ Code :

#include <iostream>
#include <cmath>
using namespace std;
int main() 
{
 cout << "\n\n Find the first 10 Lucus numbers: \n";
 cout << " -------------------------------------\n";
  cout << " The first 10 Lucus numbers are: "<<endl;

    int n = 10;  
     int n1 = 2, n2 = 1, n3;  
        if (n > 1)
		{  
            cout<<n1<<" "<<n2<<" ";
            for(int i = 2; i < n; ++i)
			{  
                n3 = n2;  
                n2 += n1;  
                n1 = n3;  
                cout<< n2 <<" ";
            } 
            cout<<endl;
        }  
        else if (n == 1)
        {
           cout<<n2<<" "; 
           cout<<endl; 
        }
        else 
        { 
            cout<<"Input a positive number."<<endl;
        }
}

Sample Output:

Find the first 10 Lucus numbers:                                                                    
 -------------------------------------                                                               
 The first 10 Lucus numbers are:                                                                     
2 1 3 4 7 11 18 29 47 76   

Flowchart:

Flowchart: Display the first 10 Lucus 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