CODEWITHSUNDEEP
mathinteger-divisionremainder
DisasterCoder
DisasterCoder

Reputation: 577

What is the remainder of integer division?

My task is to divide two variables as integer division with remainder. The problem is, that I have no clue what a “remainder” is, for now I did something like that, this is what I found by searching through the internet:

int a;
int b;
int remainder = Math.pow(a, 2) % b;

System.out.println("a^2 / b = " + Math.pow(a, 2) / b);
System.out.println("remainder = " + remainder);

If for example I set a = 43 and b = 67, I get this result:

a^2 / b = 27
remainder = 40

Now, since I have no idea what the remainder is (this is just a suggestion form the internet) I have no idea if this is the correct answer.

I was searching around about this topic but I still don't get it, if someone can elaborate I would be very thankful.

Upvotes: 19

Views: 106029

Answers (6)

Orbyfied
Orbyfied

Reputation: 154

You can use the quotient together with the remainder to calculate the count and remainder.

Here is some code that I wrote for a Minecraft plugin.

public class Division {
    public static ModuloDivResult divideMod(double a, double b) {
        double remainder = a % b;
        return new ModuloDivResult((a / b) - (remainder / b), remainder);
    }
}

We also need a container for both values.

public class ModuloDivResult {
    private double remainder;
    private double count;

    public ModuloDivResult(double count, double remainder) {
        this.remainder = remainder;
        this.count = count;
    }

    public double getRemainder() {
        return remainder;
    }

    public double getCount() {
        return count;
    }
}

Upvotes: 0

Abdel-Raouf
Abdel-Raouf

Reputation: 770

% operator will return the remainder of the Integer division.

What modules actually does under the hood ?

Modules tend to remove cycles from the number, until it reaches a positive number that is smaller than the number of the cycle which we call modulo OR a negative number which we call a reminder.

However, Using % operator is time expensive.

To avoid using % while getting the same result, we can use the following:

  • While(a >= n) a -= n; (when a is a positive number)

  • While(a < 0) a += n; (when a is a negative number)

  • a = n*q + r that means r = a - n*q While q is the integer division of a/n which means a%n == a - n * Math.toIntExact(a/n) Which is sufficient when a is a positive number.

  • While a is a negative number, we can use (a%n + n) % n Which will give you module.

Case Scenario on Clock:

if it is now 9 O'clock, what time after 4 hours => 9+4 = 13h => 13%12=1 while 12 is the cycle number in the clock

What if we need to calculate time before 24 hours (Yesterday) from now which is 9 O'clock, then: 24(2*12) => Yesterday Means 9-24 = -15h While the right answer is 9 , to solve this we will use (a%n + n) % n While a%n == (a - n * Math.toIntExact(a/n)) then -15 - 12 * Math.toIntExact(-15/12) = -3 => -3 + 12 = 9 => 9%12 => 9 - 12 * Math.toIntExact(9/12) = 9 Which is the right answer.

This is the code for the clock Scenario:

public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    int a = scanner.nextInt(); // a = -15
    int n = scanner.nextInt(); // cycle = 12

    int reminder = a - (n * Math.toIntExact(a / n));
    int reminder_plus_n = (reminder + n);
    int modulo = reminder_plus_n - (n * Math.toIntExact(reminder_plus_n / n));
    System.out.println(modulo); // Answer = 9
}

Upvotes: 0

hd1
hd1

Reputation: 34657

int remainder = a % b; will sort you. The remainder operator returns the remainder of the division.

Note that the remainder operator is also called the modulo operator. However, this is incorrect for Java as Java will return a negative value if the left operand a is negative.

Upvotes: 1

Taras Melnyk
Taras Melnyk

Reputation: 3255

    public static void main(String[] args) {
        int dividend = 139, divisor = 7;

        int quotient = dividend / divisor;
        int remainder = dividend % divisor;

        System.out.println("The Quotient is = " + quotient);
        System.out.println("The Remainder is = " + remainder);
    }

Output:

The Quotient is = 19

The Remainder is = 6

Upvotes: 9

Jo&#227;o Neves
Jo&#227;o Neves

Reputation: 1132

Yes, the % operator will return the remainder of the Integer division.

To know more about the remainder of the Integer division check out Wikipedia:

If a and d are integers, with d non-zero, it can be proven that there exist unique integers q and r, such that a = qd + r and 0 ≤ r < |d|. The number q is called the quotient, while r is called the remainder.

Upvotes: 2

SomeJavaGuy
SomeJavaGuy

Reputation: 7347

If you are looking for the mathematical modulo operation you could use

int x = -22;
int y = 24;
System.out.println(Math.floorMod(x, y));

If you are not interested in the mathematical modulo (just the remainder) then you could use

int x = -22;
int y = 24;
System.out.println(x%y);

Upvotes: 26

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