CODEWITHSUNDEEP
javado-while
Akhil Maripally
Akhil Maripally

Reputation: 109

sum of digits till the sum is one-digit number

I am a beginner java and trying to solve tricky problem

input=777
output should be 3
7+7+7=21 , 2+1=3;
From the above code if my input is 333 I am getting 9 as answer but when the sum is two digits(777=21) i am getting blank!

public static void main(String[] args) 
{

    int y=333;//if y is 777 i am getting blank
    int sum=0;
    String s;
    char []ch;
    do
    {
        s=String.valueOf(y);
        ch=s.toCharArray();

        if(ch.length>1) 
        {
            for(int i=0;i<ch.length;i++)
            {
            sum+=Character.getNumericValue(ch[i]);
            }
        }
        else
        {
        System.out.println(sum);
        }
        y=sum;      

    }while(ch.length>1);

}

Upvotes: 7

Views: 3454

Answers (8)

Gehna Anand
Gehna Anand

Reputation: 1

public static int sum_of_digits(int n) {
    return --n % 9 + 1;
}

Upvotes: 0

Tigran Babajanyan
Tigran Babajanyan

Reputation: 2025

Recursive variant

public static int myFunction(int num){
    if(num/10 == 0){
        return num;
    }

    int digitSum = num%10 + myFunction(num/10);

    if(digitSum/10 == 0){
        return digitSum;
    }

    return myFunction(digitSum);
}

Upvotes: 1

Twitter khuong291
Twitter khuong291

Reputation: 11672

You can solve this by 1 line: 

public static int sumDigits(int n) {
    return (1 + ((n-1) % 9);   
  }

For example: input 777--> return 1 + ( (777-1) % 9) = 3

Also can work with negative number.

Upvotes: 2

CharlyDelta
CharlyDelta

Reputation: 938

For a task like this, it is best practise to use recursion.

The workflow in pseudocode would look like this:

procedure sumTillOneDigit(n)
    split n into it's digits
    s := sum of all digits of n

    if s has more than one digit:
        sumTillOneDigit(s)
    else
        output s

I am intentionally writing this in pseudocode, since this should help you solving the task. I will not give you a Java implementation, as it looks like a homework to me.

For more information see:

Upvotes: 3

user902383
user902383

Reputation: 8640

I think your solution has wrong basics. There is no point to convert your number to String and handle this as char array. You are doing too much unnecessary operations.

You can do is simpler if you stick with numbers.

You can do it using recursion:

public static int sumRec(int number){
    if (number<10){
        return number;
    }
    int sum = 0;
    while(number!=0){
        sum += number %10;
        number /= 10;

    }
    return sumRec(sum);
}

or itteration

public static int sumIt(int number){
    while(number>=10){
        int sum = 0;
        while(number!=0){
            sum += number %10;
            number /= 10;
        }   
        number = sum;
    }
    return number;
}

it is much simpler, right?

Upvotes: 2

Javy
Javy

Reputation: 954

your code maybe loop forever

the right solution is the following below

public static void main(String[] args) throws ParseException {
int y = 777;// if y is 777 i am getting blank
int sum = 0;
String s;
char[] ch;
do {
    sum = 0;
    s = String.valueOf(y);
    ch = s.toCharArray();
    if (ch.length > 1) {
        for (int i = 0; i < ch.length; i++) {
            sum += Character.getNumericValue(ch[i]);
        }
    } else {
        System.out.println(ch[0]);
        break;
    }
    y = sum;
} while (ch.length > 1);
}

Maybe the better choice is the following code

public static void main(String[] args) throws ParseException {
    int y = 333;// if y is 777 i am getting blank
    int sum = 0;
    while (y % 10 != 0) {
        sum += y %10;
        y = y / 10;
        if (0 == y && sum >= 10) {
            y = sum;
            sum = 0;
        }
    }
    System.out.println(sum);
}

hope that helped

Upvotes: 5

Sumeet
Sumeet

Reputation: 8282

First of all you must reset the value of sum variable.

and secondly you must print s in else condition and not the sum and rest is fine.

public static void main(String[] args) 
{

    int y=333;//if y is 777 i am getting blank
    int sum;
    String s;
    char []ch;
    do
    {
        sum=0;
        s=String.valueOf(y);
        ch=s.toCharArray();

        if(ch.length>1) 
        {
            for(int i=0;i<ch.length;i++)
            {
            sum+=Character.getNumericValue(ch[i]);
            }
        }
        else
        {
        System.out.println(s);
        }
        y=sum;      

    }while(ch.length>1);

}

Upvotes: 2

ashishmaurya
ashishmaurya

Reputation: 1196

You are getting that because you put the print statement in else condition..

Also note that to reset your sum value before reusing it. I.e. Set sum=0 at the start of do loop.

EDIT : there are two solutions to print you value 1. Don't put you print statements inside else conditions

  1. Print sum outside the do while loop

Upvotes: 2

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