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

C++ Numbers: Exercise-38 with Solution

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

Sample Solution:

C++ Code :

#include <iostream>
using namespace std;
int main()
{
    int i,n1,r,s=0;
 cout << "\n\n Check whether a given number is palindrome or not: \n";
 cout << " -------------------------------------------------------\n";
 	cout << " Input a number: ";
    cin>>n1;	
    for(i=n1;i>0; )
    {
        r=i % 10;
        s=s*10+r;
        i=i/10;
    }
    if(s==n1)
    {
        cout<<" "<<n1<<" is a Palindrome Number."<<endl;
    }
    else
    {
        cout<<" "<<n1<<" is a not Palindrome Number."<<endl;
    }
}

Sample Output:

Check whether a given number is palindrome or not:                    
 -------------------------------------------------------               
 Input a number: 141                                                   
 141 is a Palindrome Number.

Flowchart:

Flowchart: Check whether a given number is palindrome or not

C++ Code Editor:

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Previous: Write a program in C++ to find Narcissistic decimal numbers within a specific range.
Next: Write a program in C++ to print the first 20 numbers of the Pell series.

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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