Mega Code Archive
BigDecimal quadratic
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/*
* @(#)MathUtil.java 1.0 Apr 26, 2008
*
* The MIT License
*
* Copyright (c) 2008 Malachi de AElfweald <malachid@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;
public class Util{
protected static BigInteger BigIntegerZERO = BigInteger.ZERO;
protected static BigInteger BigIntegerONE = BigInteger.ONE;
protected static BigInteger BigIntegerTWO = BigInteger.valueOf(2);
protected static BigInteger BigIntegerTHREE=BigInteger.valueOf(3);
protected static BigInteger FactorialBreakpoint = BigInteger.valueOf(96);
protected static BigDecimal BigDecimalZERO = BigDecimal.ZERO;
protected static BigDecimal BigDecimalONE = BigDecimal.ONE;
protected static BigDecimal BigDecimalTWO = new BigDecimal(2);
protected static BigDecimal BigDecimalFOUR = new BigDecimal(4);
public static BigDecimal[] quadratic(BigDecimal a, BigDecimal b, BigDecimal c, RoundingMode rounding)
{
// ax^2 + bx + c = 0
BigDecimal part1 = b.negate();
BigDecimal part2 = sqrt(b.multiply(b).subtract(BigDecimalFOUR.multiply(a).multiply(c)), rounding);
BigDecimal part3 = BigDecimalTWO.multiply(a);
BigDecimal[] toRet = new BigDecimal[2];
toRet[0] = (part1.subtract(part2)).divide(part3, RoundingMode.CEILING);
toRet[1] = (part1.add(part2)).divide(part3, RoundingMode.CEILING);
return toRet;
}
public static BigInteger sqrt(BigInteger number)
{
return sqrt(number, BigIntegerONE);
}
public static BigDecimal sqrt(BigDecimal number, RoundingMode rounding)
{
return sqrt(number, BigDecimalONE, rounding);
}
protected static BigInteger sqrt(BigInteger number, BigInteger guess)
{
// ((n/g) + g)/2: until same result twice in a row
// BigInteger result = number.divide(guess).add(guess).divide(BigIntegerTWO);
// if(result.compareTo(guess) == 0)
// return result;
//
// return sqrt(number, result);
// redoing this to avoid StackOverFlow
BigInteger result = BigIntegerZERO;
BigInteger flipA = result;
BigInteger flipB = result;
boolean first = true;
while( result.compareTo(guess) != 0 )
{
if(!first)
guess = result;
else
first=false;
result = number.divide(guess).add(guess).divide(BigIntegerTWO);
// handle flip flops
if(result.equals(flipB))
return flipA;
flipB = flipA;
flipA = result;
}
return result;
}
public static BigDecimal sqrt(BigDecimal number, BigDecimal guess, RoundingMode rounding)
{
BigDecimal result = BigDecimalZERO;
BigDecimal flipA = result;
BigDecimal flipB = result;
boolean first = true;
while( result.compareTo(guess) != 0 )
{
if(!first)
guess = result;
else
first=false;
result = number.divide(guess, rounding).add(guess).divide(BigDecimalTWO, rounding);
// handle flip flops
if(result.equals(flipB))
return flipA;
flipB = flipA;
flipA = result;
}
return result;
}
}
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