Chapter4_Loops_Ex17

/*
    ================================
            chapter 4: Loops

            Ex17: Happy number
    ================================
*/


public class MyProgram {
    public static void main(String[] args) {

        //variables
        final int SIZE=3;
        int count=0;    //count consecutive happy number
        int number=0;  //var to save the last happy number (to use outside the loop)
        boolean isHappy;

        //loop until fount 3 consecutive happy numbers
        for(int i=10,index=0;count<SIZE;i++){

           isHappy= checkNumber(i);

           //if the number is happy inc count, inc index, print msg
           if (isHappy) {
               count += 1;
               index+=1;    //index represent the how many happy numbers found
               System.out.println(index+") "+i+" is a happy number :-)");
               number=i;    //save the number i to use outside the loop
           }
           else
               count=0; //reset count
        }

        System.out.printf("%d %d %d",number-2,number-1,number); //print 3 consecutive happy numbers
    }

    //function sum the digits's power
    public static int sumPow(int number){

        //variables
        int sum=0;  //represent the sum of digit's power
        int base;  //represent single digit
        final int EXPONENT=2;

        //loop until no digits left
        while(number>0){

            base=number%10; //get single digit
            sum+=Math.pow(base,EXPONENT);   //sum the power
            number/=10; //get rid of last digit
        }

        return sum;
    }

    //function checks if the number is happy
    public static boolean checkNumber(int number){

        int sum=0;

        //loop until 1 digit number left
        do {
            sum = sumPow(number);  //getting the sum of power digits
            number=sum; // update the new number to send

        }while(sum>9);


        if (sum!=1)
            return false;   //not happy → false
        return true;    //happy number → true
    }
}