C++ program to check Happy number
In this chapter of C++ program tutorial out task is:

write a c++ program to check whether a number is happy or not using function
Program to check Happy numbers in c++
Below is the program to check happy numbers in c++ or not using if statement and loop.
/* Program Name: To check whether a number is happy or not
Program Author: Sayantan Bose
*/
#include<iostream>
using namespace std;
//For calculating the sum of square of the digits
int check(int n){
int r = 0, sum = 0;
while(n > 0){
r = n%10;
sum = sum + (r*r);
n = n/10;
}
return sum;
}
//For checking if the number is happy or not
void solve(int n)
{
int new_n = n;
while(new_n != 1 && new_n != 4){
new_n = check(new_n);
}
if(new_n == 1)
cout<<n<<" is a happy number";
else
if(new_n==4)
cout<<n<<" is not a happy number";
}
//Main function
int main()
{
int n;
cout<<"Enter the number";
cin>>n;
solve(n);
return 0;
}
OUTPUT
Enter the number
82
82 is a happy number
Or
Enter the number
3
3 is not a happy number
EXPLANATION :
In the above program to check happy numbers in c++ or not using function:

A number is said to be Happy if and only if the sum of the square of its digits is equal to one.

For example: 10 is a happy number. Because when the square of its digits are added, 1^{2}+0^{2}=1, we get 1.

In the method solve, we are checking if the sum of square of the digits are equal to one or not.

In the method, check we are calculating the sum of square of the digits and then returning it to method solve for comparing.

In the main method the input is passed on to the solve method for the operation.

If the sum turns out to be 1, its a happy number else not.
You can see the above code execution and output in codeblocks IDE:
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About the Author
Sayantan Bose
 š Iām currently working on DS Algo skills
 š± Iām currently learning web develeopement
 šÆ Iām looking to collaborate with Oppia
 š« Reach me at https://www.linkedin.com/in/sayantanbose14134a1a6/
 š Pronouns: his/him
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Published Date :
Jan 15,2021