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C++ Exercises: Check whether a given number is a Kaprekar number or not

C++ Numbers: Exercise-9 with Solution

Write a program in C++ to check whether a given number is a Kaprekar number or not.

Pictorial Presentation:

C++ Exercises: Check whether a given number is a Kaprekar number or not

Sample Solution:

C++ Code :

#include<bits/stdc++.h>
using namespace std;
 
bool chkkaprekar(int n)
{
    if (n == 1)
       return true;
    int sqr_n = n * n;
    int ctr_digits = 0;
    while (sqr_n)
    {
        ctr_digits++;
        sqr_n /= 10;
    }
    sqr_n = n*n; 
    for (int r_digits=1; r_digits<ctr_digits; r_digits++)
    {
         int eq_parts = pow(10, r_digits);

         if (eq_parts == n)
            continue;
         int sum = sqr_n/eq_parts + sqr_n % eq_parts;
         if (sum == n)
           return true;
    }
    return false;
}
int main()
{
int kpno;
 cout << "\n\n Check whether a given number is a Kaprekar number: \n";
 cout << " -------------------------------------------------------\n";
cout << " Input a number: ";
cin >> kpno;
          chkkaprekar(kpno)? cout << kpno <<" is a Kaprekar number. ": cout << kpno<<" is not a kaprekar number.";
          cout <<endl; 
}

Sample Output:

 Check whether a given number is a Kaprekar number:                    
 -------------------------------------------------------               
 Input a number: 45.                                                   
45 is a Kaprekar number. 

Flowchart:

Flowchart: Check whether a given number is a Kaprekar number or not

C++ Code Editor:

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Previous: Write a program in C++ to generate random integers in a specific range.
Next: Write a program in C++ to generate and show all Kaprekar numbers less than 1000.

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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