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C++ Exercises: Generate and show all Kaprekar numbers less than 1000

C++ Numbers: Exercise-10 with Solution

Write a program in C++ to generate and show all Kaprekar numbers less than 1000.

Pictorial Presentation:

C++ Exercises: Generate and show all Kaprekar numbers less than 1000

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()
{
 cout << "\n\n Generate and show all Kaprekar numbers less than 1000: \n";
 cout << " -----------------------------------------------------------\n";
   cout << " The Kaprekar numbers less than 1000 are: "<<endl;
   for (int i=1; i<1000; i++)
      {
          if (chkkaprekar(i))
          {
              cout << i << " ";
              
          }
          
      }
          cout <<endl; 
    return 0;
}

Sample Output:

 Generate and show all Kaprekar numbers less than 1000:                
 -----------------------------------------------------------           
 The Kaprekar numbers less than 1000 are:                              
1 9 45 55 99 297 703 999  

Flowchart:

Flowchart: Generate and show all Kaprekar numbers less than 1000

C++ Code Editor:

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

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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