Java Remainder of Integer Divison?

问题

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

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 I for example set (a = 43) and (b = 67)

Then I will get this reslut:

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..?

Thanks for any help,

Kind Regards

回答1:

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);

回答2:

    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

回答3:

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.

回答4:

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.

回答5:

% 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
}

来源：https://stackoverflow.com/questions/32778671/java-remainder-of-integer-divison

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java

math

divide