w3resource

C++ Exercises: Check whether a number is Lychrel number or not

C++ Numbers: Exercise-11 with Solution

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

Pictorial Presentation:

C++ Exercises: Check whether a number is Lychrel number or not

Sample Solution:

C++ Code :

#include <iostream>
using namespace std;


long long int numReverse(long long int number)
{
    long long int rem = 0;
    while (number > 0)
    {
    rem = (rem * 10) + (number % 10);
        number = number / 10;
    }
    return rem;
}
bool is_Palindrome(long long int num)
{
    return (num == numReverse(num));
}
bool isLychrel(int num, const int iterCount = 500)
{
    long long int temp = num;
    long long int rev;
    for (int i = 0; i < iterCount; i++)
    {
        rev = numReverse(temp);
        if (is_Palindrome(rev + temp))
            return false;
        temp = temp + rev;
    }
    return true;
}
int main()
{
int lyno;
bool l;
 cout << "\n\n Check whether a given number is a Lychrel number: \n";
 cout << " ------------------------------------------------------\n";
 cout << " Input a number: ";
 cin >> lyno;
    l = isLychrel(lyno);
    if (l==0)
    {
        cout <<" The number is not a Lychrel number."<<endl;
    }
    else
    if(l==1)
    {
        cout<<" The number is a Lychrel number."<<endl;;
    }
    return 0;
}

Sample Output:

Check whether a given number is a Lychrel number:                                                   
 ------------------------------------------------------                                              
 Input a number: 196                                                                                 
 The number is a Lychrel number.

Flowchart:

Flowchart: Check whether a number is Lychrel number or not
Flowchart: Check whether a number is Lychrel number or not
Flowchart: Check whether a number is Lychrel number or not
Flowchart: Check whether a number is Lychrel number or not

C++ Code Editor:

Contribute your code and comments through Disqus.

Previous: Write a program in C++ to generate and show all Kaprekar numbers less than 1000.
Next: Write a program in C++ to find the Lychrel numbers and the number of Lychrel number within the range 1 to 1000 (after 500 iteration).

What is the difficulty level of this exercise?



Share this Tutorial / Exercise on : Facebook and Twitter

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