HAPPY NUMBER PROGRAM IN C

In this example, you will learn a program to check whether entered number is a happy number or not.

Happy Number:

In number theory, a happy number is a number which eventually reaches 1 when replaced by the sum of the square of each digit. 

Lets consider one example!

Suppose we want to check whether 19 is happy number or not.

19 =>

1² + 9² = 82                               

8² +  2² = 68

6² + 8² = 100

1² + 0² +  0² =1

And here the sum of squares of digits ends  up with 1. Thus, 19 is happy number.

Program :

//Program to check whether given number is happy number

#include <stdio.h>

int isHappy(int);

int main( )
{
int num, result;

printf("Enter any number:");
scanf("%d",&num);
result=num;

    while(result != 1 && result !=4)
    {
        result = isHapppy(result);
    }

    if(result==1)
    {
        printf("%d is a happy number",num);
    }
    else if(result==4)
    {
        printf("%d is not a happy number",num);
    }

return 0;
}

int isHappy (int num)
{
int rem, sum=0;
    while(num>0)
    {
        rem=num%10;
        sum=sum+(rem*rem);
        num=num/10;
    }
    return sum;
}

Output:

Enter any number:19
19 is a happy number

Enter a number:79
79 is not a happy number

So that's it ! Just try this code by your own. If you have any doubts then feel free to drop a comment . I'll be happy to answer your questions .

Keep coding....