BigInteger Jacobi - Java java.math

Java examples for java.math:BigInteger

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Description

BigInteger Jacobi

Demo Code

/*//  w w w  . ja va2  s .  c  o  m
 * Copyright 2013 Valentyn Kolesnikov
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.math.RoundingMode;

public class Main{
    public static final BigInteger TWO = new BigInteger("2");
    public static final BigInteger FOUR = TWO.add(TWO);
    public static final BigInteger SEVEN = FOUR.add(THREE);
    public static final BigInteger EIGHT = FOUR.add(FOUR);
    static int Jacobi(BigInteger m, BigInteger n) {
        if (m.compareTo(n) >= 0) {
            m = m.mod(n);
            return Jacobi(m, n);
        }
        if (n.equals(BigInteger.ONE) || m.equals(BigInteger.ONE)) {
            return 1;
        }
        if (m.equals(BigInteger.ZERO)) {
            return 0;
        }
        int twoCount = 0;
        while (m.mod(TWO) == BigInteger.ZERO) {
            twoCount++;
            m = m.divide(TWO);
        }
        int J2n = n.mod(EIGHT).equals(BigInteger.ONE)
                || n.mod(EIGHT).equals(SEVEN) ? 1 : -1;
        int rule8multiplier = (twoCount % 2 == 0) ? 1 : J2n;
        int tmp = Jacobi(n, m);
        int rule6multiplier = n.mod(FOUR).equals(BigInteger.ONE)
                || m.mod(FOUR).equals(BigInteger.ONE) ? 1 : -1;
        return tmp * rule6multiplier * rule8multiplier;
    }
}

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