Digits into array

Question

I was wondering what I'm doing wrong, I tried to split the digits of an int and enter them into an array in Java. I don't know whats wrong, am I missing something when dealing with the array?

The array is declared like so:

    int[] digits = new int [100];

Here is the logic:

    while (r > 0) {
        // puts digits of n into array
        count = 0;
       sum = 0;
        while (n != 0) {
            digits[count] = n % 10;
            count++;
            n = n / 10;

        }

        // squares digits[] and populates into sum
        for (i = 0; i < count; i++) {
            sum = sum + digits[i]*digits[i];
        }

        // if sum is 1 then print 'Number is a happy number'
        if (sum == 1) {                
            addItems(b);
            r = 0;
        } else {
            r--;
        }
    }

Any help would be very much appreciated as I've been looking through the web for a few days now and haven't found any real help

You need to post more of the code. I just did ideone.com/jJcCG based on your code, and it works just fine... — corsiKa
– corsiKa, Commented Dec 21, 2011 at 22:13
What actual problem are you facing, this looks like it should work... Although, I wouldn't expect you to be able to get more than 9 or 10 digits out of an int, so your array is oversized. — Clockwork-Muse
– Clockwork-Muse, Commented Dec 21, 2011 at 22:14
Hey, I've edited my question, the code I've given you is to find if the number the user has entered is happy, I know this code works becsause I made it in C, but there must be something I need to change to make it work, any help? — David
– David, Commented Dec 21, 2011 at 22:19
@david: How is exactly is it not working? What is the expected output and how does that differ from the output that you get? — MAK
– MAK, Commented Dec 21, 2011 at 22:22
Did you try System.out.println("Number is a happy number"); in if(sum == 1) and it's not working or what? — Bhesh Gurung
– Bhesh Gurung, Commented Dec 21, 2011 at 22:29

Martijn Courteaux · Accepted Answer · 2011-12-22 00:05:51Z

2

I don't really understand your code. However this is how I would do:

public int[] intToDigitArray(int number)
{
    int numberOfDigits = (int) (Math.ceil(Math.log(number) / Math.log(10.0f)));
    int[] digits = new int[numberOfDigits];

    for (int i = 0; i < numberOfDigits; ++i)
    {
        int digit = (number % powerOfTen(i + 1)) / powerOfTen(i);
        digits[numberOfDigits - i - 1] = digit;
    }

    return digits;
}

public int powerOfTen(int exponent)
{
    if (exponent == 0) return 1;
    return 10 * powerOfTen(exponent - 1);
}

Tested, and works:

System.out.println(Arrays.toString(intToDigitArray(1234445)));

Prints:

[1, 2, 3, 4, 4, 4, 5]

answered Dec 22, 2011 at 0:05

Martijn Courteaux

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1 Comment

Maarten Bodewes Over a year ago

Are you sure this works, I copied it into a compiler and it did not work as expected. Have you made late minute changes? What about the input 0?

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