org.monte.media.math.IntMath Maven / Gradle / Ivy
/*
* @(#)IntMath.java
*
* Copyright (c) 2002-2012 Werner Randelshofer, Goldau, Switzerland.
* All rights reserved.
*
* You may not use, copy or modify this file, except in compliance with the
* license agreement you entered into with Werner Randelshofer.
* For details see accompanying license terms.
*/
package org.monte.media.math;
import java.math.BigInteger;
/**
* Utility class for integer arithmetic.
*
* @author Werner Randelshofer
* @version $Id: IntMath.java 299 2013-01-03 07:40:18Z werner $
*/
public class IntMath {
/** Creates a new instance of IntMath */
public IntMath() {
}
/**
* Returns an int whose value is the greatest common divisor of
* abs(a) and abs(b). Returns 0 if
* a==0 && b==0.
*
* @param a value with with the GCD is to be computed.
* @param b value with with the GCD is to be computed.
* @return GCD(a, b)
*/
public static int gcd(int a, int b) {
// Quelle:
// Herrmann, D. (1992). Algorithmen Arbeitsbuch.
// Bonn, München Paris: Addison Wesley.
// ggt6, Seite 63
a = Math.abs(a);
b = Math.abs(b);
while (a > 0 && b > 0) {
a = a % b;
if (a > 0) b = b % a;
}
return a + b;
}
/**
* Returns a long whose value is the greatest common divisor of
* abs(a) and abs(b). Returns 0 if
* a==0 && b==0.
*
* @param a value with with the GCD is to be computed.
* @param b value with with the GCD is to be computed.
* @return GCD(a, b)
*/
public static long gcd(long a, long b) {
// Quelle:
// Herrmann, D. (1992). Algorithmen Arbeitsbuch.
// Bonn, München Paris: Addison Wesley.
// ggt6, Seite 63
a = Math.abs(a);
b = Math.abs(b);
while (a > 0 && b > 0) {
a = a % b;
if (a > 0) b = b % a;
}
return a + b;
}
/**
* Returns a long whose value is the greatest common divisor of
* abs(a) and abs(b). Returns 0 if
* a==0 && b==0.
*
* @param a value with with the GCD is to be computed.
* @param b value with with the GCD is to be computed.
* @return GCD(a, b)
*/
public static BigInteger gcd(BigInteger a, BigInteger b) {
// Quelle:
// Herrmann, D. (1992). Algorithmen Arbeitsbuch.
// Bonn, München Paris: Addison Wesley.
// ggt6, Seite 63
a = a.abs();
b = b.abs();
while (a.compareTo(BigInteger.ZERO) > 0 && b.compareTo(BigInteger.ZERO) > 0) {
a = a.mod(b);
if (a.compareTo(BigInteger.ZERO) > 0) b = b.mod(a);
}
return a.add(b);
}
/**
* Returns an int whose value is the smallest common multiple of
* abs(a) and abs(b). Returns 0 if
* a==0 || b==0.
*
* @param a value with with the SCM is to be computed.
* @param b value with with the SCM is to be computed.
* @return SCM(a, b)
*/
public static int scm(int a, int b) {
// Quelle:
// Herrmann, D. (1992). Algorithmen Arbeitsbuch.
// Bonn, München Paris: Addison Wesley.
// gill, Seite 141
if (a == 0 || b == 0) return 0;
a = Math.abs(a);
b = Math.abs(b);
int u = a;
int v = b;
while (a != b) {
if (a < b) {
b -= a;
v += u;
} else {
a -= b;
u += v;
}
}
//return a; // gcd
return (u + v) / 2; // scm
}
/**
* Returns an int whose value is the smallest common multiple of
* abs(a) and abs(b). Returns 0 if
* a==0 || b==0.
*
* @param a value with with the SCM is to be computed.
* @param b value with with the SCM is to be computed.
* @return SCM(a, b)
*/
public static long scm(long a, long b) {
// Quelle:
// Herrmann, D. (1992). Algorithmen Arbeitsbuch.
// Bonn, München Paris: Addison Wesley.
// gill, Seite 141
if (a == 0 || b == 0) return 0;
a = Math.abs(a);
b = Math.abs(b);
if (b==1)return a;
if (a==1)return b;
long u = a;
long v = b;
// FIXME - Handle overflow
while (a != b) {
if (a < b) {
b -= a;
v += u;
} else {
a -= b;
u += v;
}
}
//return a; // gcd
return (u + v) / 2; // scm
}
/**
* Returns an int whose value is the smallest common multiple of
* abs(a) and abs(b). Returns 0 if
* a==0 || b==0.
*
* @param a value with with the SCM is to be computed.
* @param b value with with the SCM is to be computed.
* @return SCM(a, b)
*/
public static BigInteger scm(BigInteger a, BigInteger b) {
// Quelle:
// Herrmann, D. (1992). Algorithmen Arbeitsbuch.
// Bonn, München Paris: Addison Wesley.
// gill, Seite 141
if (a.compareTo(BigInteger.ZERO) == 0 || b.compareTo(BigInteger.ZERO) == 0) {
return BigInteger.ZERO;
}
a = a.abs();
b = b.abs();
if (b.compareTo(BigInteger.ONE)==0)return a;
if (a.compareTo(BigInteger.ONE)==0)return b;
BigInteger u = a;
BigInteger v = b;
// FIXME - Handle overflow
while (a.compareTo(b) != 0) {
if (a .compareTo( b)<0) {
b = b.subtract(a);
v = v.add(u);
} else {
a = a.subtract(b);
u = u.add(v);
}
}
//return a; // gcd
return (u.add(v)).divide(BigInteger.valueOf(2)); // scm
}
/**
* Reverses all 32 bits of the provided integer value.
*/
public static int reverseBits(int a) {
return reverseBits(a, 32);
}
/**
* Reverses specified number of bits of the provided integer value.
* @param a The number.
* @param numBits The number of bits (must be between 1 and 32).
*/
public static int reverseBits(int a, int numBits) {
int b = 0;
for (int i=0; i < numBits; i++) {
b <<= 1;
b |= (a & 1);
a >>>= 1;
}
return b;
}
public static void main(String[] args) {
for (int i=0; i < 8; i++) {
int a = 1<© 2015 - 2025 Weber Informatics LLC | Privacy Policy