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C++ Exercises: Check whether a number is a Duck Number or not

C++ Numbers: Exercise-26 with Solution

Write a program in C++ to check whether a number is a Duck Number or not.

Pictorial Presentation:

C++ Exercises: Check whether a number is a Duck Number or not

Sample Solution:

C++ Code :

# include <bits/stdc++.h>
using namespace std;

int main()
{
    int dno,dkno,r,flg;
	flg=0;
 cout << "\n\n Check whether a number is a Duck Number or not: \n";
 cout << " ----------------------------------------------------\n";
 cout << " Input a number: ";
 cin >> dkno;
 dno=dkno;
    while(dkno>0)
        {
            if(dkno % 10 == 0)
            {
            flg=1;
            break;
            }
			dkno/=10;
        }
            if(dno>0 && flg==1)
            {
            cout << " The given number is a Duck Number."<<endl;
            }
            else
            {
            cout << " The given number is not a Duck Number."<<endl;
            }
}

Sample Output:

Check whether a number is a Duck Number or not:                       
 ----------------------------------------------------                  
 Input a number: 30                                                    
 The given number is a Duck Number. 

Flowchart:

Flowchart: Check whether a number is a Duck Number or not

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