/**
* Write a Java program to find and print the Happy numbers between m and n.
Happy number: Starting with any positive integer, replace the number by the sum of the squares of its digits,
and repeat the process until the number equals 1, or it loops endlessly in a cycle which does not include 1.
Example: 19 is a happy number
1^2 + 9^2=82
8^2 + 2^2=68
6^2 + 8^2=100
1^2 + 0^2 + 02=1
The first few happy numbers are 1, 7, 10, 13, 19, 23, 28, 31, 32, 44, 49, 68, 70, 79, 82, 86, 91, 94, 97, 100, ...
*/
import java.util.*;
public class HappyNum
{
public static int digitSq(int x) // recursive function to find square of digits of the number
{
if(x<10)
return x*x;
else
return (x%10)*(x%10) + digitSq(x/10);
} // end of digitSq()
public static boolean isHappy(int num, int i) // recursive function to check whether the no. is happy or not
{
//System.out.println(num);
if(num==1)
return true;
else if(i==15)
return false;
else
return isHappy( digitSq(num), i+1);
} // end of isHappy()
public static void main()
{
Scanner sc=new Scanner(System.in);
System.out.print("\nEnter lower limit : ");
int m=sc.nextInt();
System.out.print("\nEnter upper limit : ");
int n=sc.nextInt();
System.out.println("The Happy numbers are : ");
for(int i=m;i<=n;i++)
{
if( isHappy(i, 0) )
{
System.out.print(i+" ");
}
}
} // end of main()
} // end of class
Q.10 WAP in C/ C++/ java to check whether a number is a Harshad Number or not. In recreational mathematics, a Harshad number in a given number base is an integer that is divisible by the sum of its digits when written in that base. Example: Number 200 is a Harshad Number because the sum of digits 2 and 0 and 0 is 2(2+0+0) and 200 is divisible by 2. Number 171 is a Harshad Number because the sum of digits 1 and 7 and 1 is 9(1+7+1) and 171 is divisible by 9. Solution : #include <stdio.h> int sumofdigits ( int x) // function to compute sum of digits { int sum = 0 ; while (x > 0 ) { sum += x % 10 ; x = x / 10 ; } return sum ; } void main () { int n , sod ; printf ( " \n Enter any positive number : " ); scanf ( " %d " , & n ); if ( n < 0 ) { printf ( " \n Invalid input! Enter the value again -->" ); main (); // calls the m
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