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C++ Exercises: Display the first 10 Catlan numbers

C++ Numbers: Exercise-15 with Solution

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

Pictorial Presentation:

C++ Exercises: Display the first 10 Catlan numbers

Sample Solution:

C++ Code :

#include<iostream>
using namespace std;
unsigned long int cataLan(unsigned int n)
{
    if (n <= 1) return 1;
    unsigned long int catno = 0;
    for (int i=0; i<n; i++)
        catno += cataLan(i)*cataLan(n-i-1);
    return catno;
}
int main()
{
 cout << "\n\n Find the first 10 Catlan numbers: \n";
 cout << " --------------------------------------\n";
  cout << " The first 10 Catlan numbers are: "<<endl;
    for (int i=0; i<10; i++)
        cout << cataLan(i) << " ";
  cout <<endl;		
    return 0;
}

Sample Output:

 Find the first 10 Catlan numbers:                                                                   
 --------------------------------------                                                              
 The first 10 Catlan numbers are:                                                                    
1 1 2 5 14 42 132 429 1430 4862

Flowchart:

Flowchart: Display the first 10 Catlan 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