How to get even/odd random number divisible by first random number

Question

I have following code:

        quesPart1 = ran.nextInt((numbersBetween - 2) + 1) + 2;
        quesPart2 = ran.nextInt((numbersBetween - 2) + 1) + 2;
        if(quesPart2 > quesPart1)
        {
            int placeHolder = quesPart1;
            quesPart1 = quesPart2;
            quesPart2 = placeHolder;                    
        }
        //if first part is even
        if(quesPart1 % 2 == 0)
        {
            if(quesPart2  % 2 != 0)
            {
                --quesPart2;
            }
        }
        else
        {
            if(quesPart2 % 2 == 0)
            {
                ++quesPart2;
            }
        }

Above code make sure that if quesPart1 is greater than quesPart2 and both are even or both are odd numbers. Now i want to get only random numbers which are also divisible by one another. Like if i divide quesPart1 by quesPart2 i get integer not decimal number. Any ideas how i can do that without adding too much complexity to above code.

Answer 1

Like if i divide quesPart1 by quesPart2 i get integer not decimal number.

Keep it simple: generate random numbers and take their product. Example:

quesPart2 = ran.nextInt(UPPER_BOUND);
int temp = ran.nextInt(UPPER_BOUND);
questPart1 = temp * quesPart2;

Specifying the range, as in the original question, is left an an exercise to the reader. (What, you didn't think I was going to do all the thinking for you, did you? ;-)

Answer 2

Look into the modulus operator, a % b . It returns the left over amount when a is divided by b. When b cleanly divides into a, such that there is no decimal part, a % b will be zero.

In order to generate a number that is divisible by another, given two random numbers, a and b , simply multiply a by b . This will give you c , a number that is a multiple of both a and b , and therefore dividable by both cleanly without remainder.

Answer 3

You can do something like:

int div = quesPart1 / quesPart2;
quesPart1 = div * quesPart2;

add this code at the bottom of your code.

Answer 4

I have come up with this simple function and a do while loop that is easy to implement.

// This is a simple function to set the min and max integers you want
    const getRandomIntInclusive = (min, max) => {
          min = Math.ceil(min);
          max = Math.floor(max);
          return Math.floor(Math.random() * (max - min + 1)) + min;
        }
        //Define some variables variables
        let firstNo = 0
        let secondNo = 0
        let isDivisible = 0;
        //generate random ints until first number is divisible to second number
        do {
           //get random int between 1-9 for the first and second integer
           firstNo = getRandomIntInclusive(1, 9) 
           secondNo = getRandomIntInclusive(1, 9)
           isDivisible = firstNo % secondNo;  //Check if it's fully divisible
           }
           while (isDivisible != 0)      //Run until it is fully divisible

Answer 5

To generate Random numbers in java you can use ran.nextInt() or please refer to this link to see how to generate random numbers. store those 2 random numbers (as num1 and num2).

To verify whether the solution after dividing num1 and num2 is integer or not, use this method:

sol = num1 / num2
if (sol == (int)sol)
{
   ... //true if the solution is an integer
}