BigInteger Modulo '%' Operation & Less Tha

问题:

Hi I have an algorithm in which I need to apply operations to BigInt's.

I understand that BigInt's can be manipulated using the Maths class such as:

import java.math.*;

BigInteger a;
BigInteger b = BigInteger.ZERO;
BigInteger c = BigInteger.ONE;
BigInteger d = new BigInteger ("3");
BigInteger e = BigInteger.valueOf(5);

a.multiply(b);
a.add(b);
a.substract(b);
a.divide(b);

I need to be able to apply greater than for a while condition e.g.

while (a > 0) {

Which gives me a syntax error saying "bad operand types for binary operator '>', first type: java.math.BigInteger, second type: int.

I also need to be able to apply the modulo (%) operator to a BigInteger.

b = a % c;

Can anyone suggest a way of doing this?

If there isn't a solution then I'm just going to have to somehow manipulate my BigInteger into an unique Long using a reduce function (which is far from ideal).

Silverzx.

回答1:

To compare BigInteger, use BigInteger.compareTo.

while(a.compareTo(BigInteger.ZERO) > 0)
    //...

And for modulo (%), use BigInteger.mod.

BigInteger blah = a.mod(b);

回答2:

For comparing BigIntegers you may use compareTo, but in the special case when you compare to 0 the signum method will also do the job(and may be a bit faster). As for taking the remainder of a given division you may use the method mod(better option here) or alternatively use divideAndRemainder which returns an array with both the result of the division and the remainder.