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C++ Exercises: Check a number is a Happy or not

C++ Numbers: Exercise-16 with Solution

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

Sample Solution:

C++ Code :

#include <bits/stdc++.h>
using namespace std;
int SumOfSquNum(int givno)
{
    int SumOfSqr = 0;
    while (givno)
    {
        SumOfSqr += (givno % 10) * (givno % 10);
        givno /= 10;
    }
    return SumOfSqr;
}
bool checkHappy(int chkhn)
{
    int slno, fstno;
    slno = fstno = chkhn;
    do
    {
        slno = SumOfSquNum(slno);
        fstno = SumOfSquNum(SumOfSquNum(fstno));
    }
    while (slno != fstno);
    return (slno == 1);
}
int main()
{
int hyno;
 cout << "\n\n Check whether a number is Happy number or not: \n";
 cout << " ---------------------------------------------------\n";
 cout << " Input a number: ";
 cin >> hyno;

    if (checkHappy(hyno))
        cout << hyno << " is a Happy number\n";
    else
        cout << hyno << " is not a Happy number\n";
}

Sample Output:

 Check whether a number is Happy number or not:                                                      
 ---------------------------------------------------                                                 
 Input a number: 23                                                                                  
23 is a Happy number

Flowchart:

Flowchart: Display the first 10 catlan numbers
Flowchart: Display the first 10 catlan numbers
Flowchart: Display the first 10 catlan numbers

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