SelfDivisor is #1 from the from the 2007 AP Computer Science A Free Response problems.

https://secure-media.collegeboard.org/secure/ap/pdf/computer-science-a/ap-2007-computer-science-a-free-response-questions.pdf

Part (a) isSelfDivisor method

public static boolean isSelfDivisor(int number)
{
    if(number == 0)
        return false;

    int numRemaining = number;

    while(numRemaining > 0)
    {
        int digit = numRemaining % 10;

        if(digit == 0 || number % digit != 0)
            return false;

        numRemaining /= 10;
    }

    return true;
}

See Division operations for discussion of using integer division (/) and modular division (%).

Part (b) firstNumSelfDivisors method

public static int[] firstNumSelfDivisors(int start, int num)
{
    int[] selfDivisors = new int[num];

    int possible = start;
    int i = 0;

    while(i < selfDivisors.length)
    {
        if(isSelfDivisor(possible))
        {
            selfDivisors[i] = possible;
            i++;
        }

        possible++;
    }

    return selfDivisors;
}

2007 AP CS Exam Free Response Solutions

• StudentAnswerSheet Free Response Solution
• GameState Free Response Solution

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