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# 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, 12+02=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: CPP Programs

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