Polynomial Data Structure
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/* | |
* Question: Create a data structure to represent polynomial addition and substraction | |
* Run the code online: http://ideone.com/s5qjU | |
*/ | |
import static org.junit.Assert.*; | |
import org.junit.Test; | |
import java.util.*; | |
public class PolynomialTest | |
{ | |
public static class Term | |
implements Cloneable | |
{ | |
int coefficient; | |
int power; | |
public Term(int coefficient, int power) { | |
this.coefficient = coefficient; | |
this.power = power; | |
} | |
public String toString() { | |
StringBuffer display = new StringBuffer(); | |
if (power == 0) { | |
display.append(coefficient); | |
} | |
else if (power > 0) { | |
if (coefficient != 1) display.append(coefficient); | |
display.append('x'); | |
if (power > 1) display.append('^').append(power); | |
} | |
return display.toString(); | |
} | |
public Term add(Term other) { | |
if (this.power == other.power) this.coefficient += other.coefficient; | |
return this; | |
} | |
protected Object clone() { | |
Term term = new Term(this.coefficient,this.power); | |
return term; | |
} | |
public boolean equals(Object o) { | |
if (!(o instanceof Term)) return false; | |
Term other = (Term)o; | |
return this.coefficient == other.coefficient && this.power == other.power; | |
} | |
} | |
public static class Polynomial | |
{ | |
Map<Integer,Term> terms; | |
public Polynomial() { | |
this.terms = new TreeMap<Integer,Term>(); | |
} | |
public Polynomial(Collection<Term> list) { | |
this(); | |
for (Term term : list) this.add((Term)term.clone()); | |
} | |
public Polynomial add(Term other) { | |
Term term = terms.get(other.power); | |
terms.put(other.power,(term == null) ? other : term.add(other)); | |
return this; | |
} | |
public Polynomial add(int coefficient, int power) { | |
add(new Term(coefficient,power)); | |
return this; | |
} | |
public Polynomial add(Polynomial other) { | |
Polynomial poly = new Polynomial(getTerms()); | |
for (Term term : other.getTerms()) poly.add(term); | |
return poly; | |
} | |
public void plus(Polynomial other) { | |
for (Term term : other.getTerms()) this.add(term); | |
} | |
public Polynomial multiply(Polynomial other) { | |
Polynomial poly = new Polynomial(); | |
for (Term first : this.getTerms()) { | |
Polynomial current = new Polynomial(); | |
for (Term second : other.getTerms()) { | |
Term product = new Term(first.coefficient*second.coefficient,first.power+second.power); | |
current.add(product); | |
} | |
poly.plus(current); | |
} | |
return poly; | |
} | |
public String toString() { | |
StringBuffer display = new StringBuffer(); | |
int count = 0; | |
for (Term term : getTerms()) { | |
display.append(term.toString()); | |
if (count<terms.size()-1) display.append('+'); | |
count++; | |
} | |
return display.toString(); | |
} | |
public Collection<Term> getTerms() { | |
return this.terms.values(); | |
} | |
public boolean equals(Object o) { | |
if (!(o instanceof Polynomial)) return false; | |
Polynomial other = (Polynomial)o; | |
return this.terms.equals(other.terms); | |
} | |
} | |
// x^2 + 2x | |
// + 1x + 2 | |
//---------------- | |
// x^2 + 3x + 2 | |
@Test public void testPolynomialAddition1() | |
{ | |
System.out.println(); | |
Polynomial first = new Polynomial().add(new Term(1,2)).add(new Term(2,1)); | |
Polynomial second = new Polynomial().add(new Term(1,1)).add(new Term(2,0)); | |
Polynomial expect = new Polynomial().add(new Term(1,2)).add(new Term(3,1)).add(new Term(2,0)); | |
Polynomial output = first.add(second); | |
System.out.println("first = "+first); | |
System.out.println("second = "+second); | |
System.out.println("sum = "+output); | |
assertEquals(expect,output); | |
} | |
// x + 1 | |
// + x + 2 | |
//--------------- | |
// 2x + 3 | |
@Test public void testPolynomialAddition2() | |
{ | |
System.out.println(); | |
Polynomial first = new Polynomial().add(new Term(1,1)).add(new Term(1,0)); | |
Polynomial second = new Polynomial().add(new Term(1,1)).add(new Term(2,0)); | |
Polynomial expect = new Polynomial().add(new Term(2,1)).add(new Term(3,0)); | |
Polynomial output = first.add(second); | |
System.out.println("first = "+first); | |
System.out.println("second = "+second); | |
System.out.println("sum = "+output); | |
assertEquals(expect,output); | |
} | |
// x + 1 | |
// * x + 2 | |
// ------------------------- | |
// x*(x + 2) + 1*(x + 2) | |
// x^2 + 2x + x + 2 | |
// x^2 + 3x + 2 | |
@Test public void testPolynomialMultiply() | |
{ | |
System.out.println(); | |
Polynomial first = new Polynomial().add(new Term(1,1)).add(new Term(1,0)); | |
Polynomial second = new Polynomial().add(new Term(1,1)).add(new Term(2,0)); | |
Polynomial output = first.multiply(second); | |
Polynomial expect = new Polynomial().add(new Term(1,2)).add(new Term(3,1)).add(new Term(2,0)); | |
System.out.println("first = "+first); | |
System.out.println("second = "+second); | |
System.out.println("product = "+output); | |
assertEquals(expect,output); | |
} | |
} |
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