问题描述
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嘿，我正在用Java编写多项式的复合方法，并且遇到了一些问题。到目前为止，这是我的代码，我只是迷路了...
public class Polynomial
{
final static private int mantissa = 52;
final static private double epsilon = Math.pow(2.0,-mantissa);
private double coefficient = 0.0;
private int power = 0;
private Polynomial successor = null;
public Polynomial(double coefficient,int power)
{
if (Double.isNaN(coefficient))return;
if (Math.abs(coefficient) < epsilon)return;
if (power < 0)return;
this.coefficient = coefficient;
this.power = power;
}
/* conditions
this(X) => sum(coefficient(i)*X^i:for(i=degree;i>=0;i--)) && X^0=1
this.degree()==this.power==highestPower
this.highestPoweredCoefficient==this.coefficient
this.successor!=null links to terms whose powers uniquely decrease
Polynomial(0.0,0)=(coefficient=0.0,power=0,successor=null)==0.0
if (coefficient==NaN) coefficient=0.0
if (abs(coefficient)<epsilon)) coefficient=0.0
if (power<0) power=0
if (this.degree()==0) abs(coefficient(0))>=0.0
if (this.degree()>0) abs(coefficient(i))>=epsilon for all i>=0
*/
private static void add(Polynomial polynomial,double coefficient,int power)
{
// This part is given to us
if (polynomial == null) return;
if (Math.abs(coefficient) < epsilon) coefficient = 0.0;
if (coefficient == 0.0) return;
if (power < 0) return;
// End of given code.
if (polynomial.coefficient == 0.0)
{
polynomial.coefficient = coefficient;
polynomial.power = power;
return;
}
if (polynomial.power == power)
{
polynomial.coefficient += coefficient;
if (Math.abs(polynomial.coefficient) < epsilon)
polynomial.coefficient = 0.0;
if (polynomial.coefficient != 0.0 || polynomial.power == 0) return;
if (polynomial.successor == null)
{
polynomial.power = 0;
return;
}
polynomial.coefficient = polynomial.successor.coefficient;
polynomial.power = polynomial.successor.power;
polynomial.successor = polynomial.successor.successor;
return;
}
// sets up variables used.
Polynomial old = null;
Polynomial checker = polynomial;
// goes through polynomial looking for the right place.
while (checker != null)
{
if (checker.power <= power)
{
break; //breaks the loop
}
old = checker;
checker = checker.successor;
}
//
if (old == null)
{
Polynomial node = new Polynomial(0.0,0); //creates a new node for insertion
node.coefficient = polynomial.coefficient;
node.power = polynomial.power;
node.successor = polynomial.successor;
polynomial.coefficient = coefficient;
polynomial.power = power;
polynomial.successor = node;
return;
}
//
if (checker == null || checker.power < power)
{
Polynomial node = new Polynomial(0.0,0); //sets a node for insertion
node.coefficient = coefficient;
node.power = power;
node.successor = checker;
old.successor = node;
return;
}
coefficient += checker.coefficient;
if (Math.abs(coefficient) < epsilon) coefficient = 0.0;
if (coefficient == 0.0)
old.successor = checker.successor;
else
checker.coefficient = coefficient;
}
final public int cardinality() {
int count = 1;
Polynomial traverser = this.successor;
while (traverser != null)
{ //THIS METHOD IS GIVEN TO US!
count++;
traverser = traverser.successor;
}
return count;
}
final public Polynomial clone() {
Polynomial result = new Polynomial(0.0,0);
result.coefficient = this.coefficient;
result.power = this.power;
Polynomial traverserThis = this;
Polynomial traverserResult = result; //THIS METHOD IS GIVEN TO US!
while (traverserThis.successor != null) {
traverserResult.successor = new Polynomial(0.0,0);
traverserThis = traverserThis.successor;
traverserResult = traverserResult.successor;
traverserResult.coefficient = traverserThis.coefficient;
traverserResult.power = traverserThis.power;
}
return result;
}
final public double coefficient(int power) {
if (power < 0) {
return 0.0;
}
Polynomial traverser = this;
do {
if (traverser.power < power) {
return 0.0;
}
if (traverser.power == power) { //THIS METHOD IS GIVEN TO US
return traverser.coefficient;
}
traverser = traverser.successor;
} while (traverser != null);
return 0.0;
}
//Method done by Callum
final public Polynomial composite(Polynomial that)
{
if (that == null)
{
return null;
}
Polynomial result = new Polynomial(0.0,0); //the result polynomial
Polynomial current = this.clone(); //current is a copy of \'this\' used for moving through
// the loop.
Polynomial tempHolder2 = that;
Polynomial tempHolder = new Polynomial(0.0,0); //just a temporary holding polynomial
Polynomial thatNew = that.clone(); //another clone used for iteration.
while(current != null)
{
for( int i = 1; i <= current.power; i++)
{
tempHolder2 = tempHolder2.times(thatNew);
}
tempHolder.coefficient = current.coefficient;
tempHolder = tempHolder.times(tempHolder2);
current = current.successor; //Moves to next one
result = result.plus(tempHolder); //adds the values?
tempHolder = new Polynomial(0.0,0); //resets it for next use
}
return result;
}
final public int degree()
{
return this.power; //THIS METHOD WAS GIVEN TO US!
}
//METHOD DONE BY Mitchell Bowie
final public Polynomial differentiate()
{
Polynomial result = new Polynomial (0.0,0); //The result polynomial
Polynomial polynomial = this; //THIS polynomial. current one being assessed.
if (polynomial.power==0)
{
result.coefficient = (0.0); //returns 0.0 if its power = 0
return result;
}
Polynomial temp = new Polynomial (0.0,0); // just a polynomial used to add things up
while (polynomial != null) //goes through the polynomial
{
temp.coefficient = (polynomial.power*(polynomial.coefficient));
temp.power = (polynomial.power -1);
add (result,temp.coefficient,temp.power); //adds the new values to a polynomial
polynomial = polynomial.successor; //increments the polynomial //named result
}
return result; //returns the value added in the while loop
}
final public Polynomial[] dividedBy(Polynomial that)
{
//THIS METHOD WAS TOO HARD!!!!!
Polynomial[] polynomials={that};
return polynomials;
}
final public boolean equals(Polynomial that)
{
if (that == null) {
return false;
}
if (this.coefficient != that.coefficient) {
return false;
}
if (this.power != that.power) {
return false;
}
if (this.successor == null && that.successor == null) { //THIS METHOD WAS GIVEN TO US!
return true;
}
if (this.successor == null && that.successor != null) {
return false;
}
if (this.successor != null && that.successor == null) {
return false;
}
return this.successor.equals(that.successor);
}
//Method done by Mitchell
final public double evaluate(double variable)
{
if (Double.isNaN(variable)) { //THIS IS ALL GIVEN
variable = 0.0;
}
if (Math.abs(variable) < epsilon) {
variable = 0.0;
}
double value = 0.0;
//END OF GIVEN STUFF
Polynomial current = this.clone(); //creates a copy of this
while(current !=null) //goes through the copy until null
{
if(current.power > 0) //checks if power > 0
{
value += current.coefficient * Math.pow(variable,current.power);
}
else //if its not then it will do this!
{
value += current.coefficient; //adds the coefficient
}
current = current.successor; //iterates the loop
}
return value;// returns the value
}
//Method done by Mitchell and Callum
final public Polynomial integrate()
{
if (this.coefficient == 0.0)
{
return new Polynomial(0.0,0); //Given part
}
Polynomial result = this.clone(); //why it was called result i dont know but this threw me
//for a long time. -.-
// End of given stuff
Polynomial result2 = new Polynomial(0.0,0);
Polynomial tempHolder = new Polynomial(0.0,0); //just holds temp values
while(result!=null)
{
tempHolder.coefficient = result.coefficient / (result.power +1);
tempHolder.power = result.power + 1; //adds 1 to the power of result and sets it to
//tempHolder
result2 = result2.plus(tempHolder);
result = result.successor; //iterates the loop
}
return result2; //returns result2 NOT result -.-
}
final public Polynomial minus(Polynomial that)
{
if (that == null) {
return null;
}
if (this.equals(that)) {
return new Polynomial(0.0,0);
}
Polynomial result = this.clone(); //THIS METHOD WAS GIVEN
if (that.coefficient == 0.0) {
return result;
}
Polynomial traverser = that;
do {
add(result,-traverser.coefficient,traverser.power);
traverser = traverser.successor;
} while (traverser != null);
return result;
}
final public Polynomial plus(Polynomial that)
{
if (that == null) {
return null;
}
if (this.coefficient == 0.0) {
return that.clone();
}
Polynomial result = this.clone(); //THIS METHOD WAS GIVEN TO US!
if (that.coefficient == 0.0) {
return result;
}
Polynomial traverser = that;
do {
add(result,traverser.coefficient,traverser.power);
traverser = traverser.successor;
} while (traverser != null);
return result;
}
final public int powerMax()
{
int max = Integer.MIN_VALUE;
Polynomial traverser = this;
do {
if (max < traverser.power) { //THIS METHOD WAS GIVEN TO US!
max = traverser.power;
}
traverser = traverser.successor;
} while (traverser != null);
return max;
}
final public int powerMin()
{
int min = Integer.MAX_VALUE;
Polynomial traverser = this;
do {
if (min > traverser.power) { //THIS METHOD WAS GIVEN TO US!
min = traverser.power;
}
traverser = traverser.successor;
} while (traverser != null);
return min;
}
//TIMES METHOD BY Callum
//Take current polynomial and times it by that polynomial.
//Uses dual while loops to get the results needed.
final public Polynomial times(Polynomial that)
{
Polynomial result = new Polynomial (0.0,0);
Polynomial thiss = this;
int count = 0;
if (that == null)return null;
Polynomial newThat = that.clone(); //creates a clone of that
int length = that.cardinality();
if (thiss.coefficient == 0.0)
{
return result; //if this coefficient is 0.0 return 0.0
}
if (that.coefficient == 0.0)
{
return result; //if that coefficient is 0.0 return 0.0
}
while (thiss != null) //goes through thiss until its null
{
double thissc = thiss.coefficient; //sets the double to the coefficient
int thissp = thiss.power; //sets the int to the power
while (that !=null) //goes through that until null
{
double thatc = that.coefficient; //sets the double to that coefficient
int thatp = that.power; //sets the int to that power
double resultc = thissc*thatc; // sets the result double to this coeff times that coeff
int resultp = thissp+thatp; // sets the result int to this power plus that power
if (count == 0) //if its the first value in the result it will just override the values
{
result.coefficient = resultc; //sets the coeff
result.power = resultp; //sets the power
}
else
{
add(result,resultc,resultp); //adds the values to the result polynomial with add method
}
count++; //count increase so it doesnt over ride the values
that = that.successor; //iterates the inner loop!
}
that = newThat; //resets that to the start for next loop iteration!
thiss = thiss.successor; //iterates the loop!
}
return result; //returns what is in result!
}
final public String toString()
{
String string = \"\" + this.coefficient + (this.power == 0 ? \"\" : \"*X^\" + this.power);
Polynomial traverser = this.successor;
while (traverser != null) {
string += (traverser.coefficient > 0.0 ? \"+\" : \"\") //THIS METHOD WAS GIVENT TO US!
+ traverser.coefficient
+ (traverser.power == 0 ? \"\" : \"*X^\"
+ traverser.power);
traverser = traverser.successor;
}
return string;
}
}
解决方法
我将从Monomial开始：
package poly;
public class Monomial
{
private final double coeff;
private final int expon;
public Monomial()
{
this(0.0,0);
}
public Monomial(double coeff)
{
this(coeff,0);
}
public Monomial(double coeff,int expon)
{
this.coeff = coeff;
this.expon = expon;
}
public double getCoeff()
{
return coeff;
}
public int getExpon()
{
return expon;
}
public Monomial add(Monomial other)
{
if (this.expon != other.expon)
throw new IllegalArgumentException(\"Exponents must match in order to add\");
return new Monomial((this.coeff+other.coeff),this.expon);
}
public Monomial sub(Monomial other)
{
if (this.expon != other.expon)
throw new IllegalArgumentException(\"Exponents must match in order to subtract\");
return new Monomial((this.coeff-other.coeff),this.expon);
}
public Monomial mul(Monomial other)
{
return new Monomial((this.coeff*other.coeff),(this.expon+other.expon));
}
public Monomial div(Monomial other)
{
return new Monomial((this.coeff/other.coeff),(this.expon-other.expon));
}
@Override
public boolean equals(Object o)
{
if (this == o)
{
return true;
}
if (o == null || getClass() != o.getClass())
{
return false;
}
Monomial monomial = (Monomial) o;
if (Double.compare(monomial.coeff,coeff) != 0)
{
return false;
}
if (expon != monomial.expon)
{
return false;
}
return true;
}
@Override
public int hashCode()
{
int result;
long temp;
temp = coeff != +0.0d ? Double.doubleToLongBits(coeff) : 0L;
result = (int) (temp ^ (temp >>> 32));
result = 31 * result + expon;
return result;
}
@Override
public String toString()
{
final StringBuilder sb = new StringBuilder();
if (coeff != 1.0) sb.append(coeff);
if (expon != 0) {
sb.append(\'x\');
if (expon != 1) sb.append(\'^\').append(expon);
}
return sb.toString();
}
}
package poly;
import org.junit.Assert;
import org.junit.Test;
public class MonomialTest
{
private static final double DELTA = 0.001;
@Test
public void testConstructor_Default()
{
Monomial test = new Monomial();
Assert.assertEquals(\"0.0\",test.toString());
}
@Test
public void testConstructor_Constant()
{
Monomial test = new Monomial(2);
Assert.assertEquals(\"2.0\",test.toString());
}
@Test
public void testConstructor()
{
Monomial test = new Monomial(6,3);
Assert.assertEquals(\"6.0x^3\",test.toString());
Assert.assertEquals(6.0,test.getCoeff(),DELTA);
Assert.assertEquals(3,test.getExpon());
}
@Test
public void testAddSuccess()
{
Monomial x = new Monomial(2,3);
Monomial y = new Monomial(3,3);
Monomial expected = new Monomial(5,3);
Assert.assertEquals(expected,x.add(y));
}
@Test(expected = IllegalArgumentException.class)
public void testAdd_MismatchedExponents()
{
Monomial x = new Monomial(2,4);
x.add(y);
}
@Test
public void testSubSuccess()
{
Monomial x = new Monomial(2,3);
Monomial expected = new Monomial(-1,x.sub(y));
}
@Test(expected = IllegalArgumentException.class)
public void testSub_MismatchedExponents()
{
Monomial x = new Monomial(2,4);
x.sub(y);
}
@Test
public void testMulSuccess()
{
Monomial x = new Monomial(2,3);
Monomial expected = new Monomial(6,6);
Assert.assertEquals(expected,x.mul(y));
}
@Test
public void testDivSuccess()
{
Monomial x = new Monomial(4,4);
Monomial y = new Monomial(2,3);
Monomial expected = new Monomial(2,1);
Assert.assertEquals(expected,x.div(y));
}
@Test
public void testEquals_null()
{
Monomial x = new Monomial();
Assert.assertFalse(x.equals(null));
}
@Test
public void testEquals_reflexive()
{
Monomial x = new Monomial(2,3);
Assert.assertTrue(x.equals(x));
}
@Test
public void testEquals_symmetric()
{
Monomial x = new Monomial(2,3);
Monomial y = new Monomial(2,3);
Assert.assertTrue(x.equals(y) && y.equals(x));
Assert.assertEquals(x.hashCode(),y.hashCode());
}
@Test
public void testEquals_transitive()
{
Monomial x = new Monomial(2,3);
Monomial z = new Monomial(2,3);
Assert.assertTrue(x.equals(y) && y.equals(z) && z.equals(x));
Assert.assertEquals(x.hashCode(),y.hashCode());
Assert.assertEquals(y.hashCode(),z.hashCode());
Assert.assertEquals(z.hashCode(),x.hashCode());
}
@Test
public void testEquals_differentCoefficients()
{
Monomial x = new Monomial(2,3);
Assert.assertFalse(x.equals(y));
Assert.assertFalse(x.hashCode() == y.hashCode());
}
@Test
public void testEquals_differentExponents()
{
Monomial x = new Monomial(2,4);
Assert.assertFalse(x.equals(y));
Assert.assertFalse(x.hashCode() == y.hashCode());
}
}
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