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# thiago1186's solution

## to Pythagorean Triplet in the Java Track

Published at Nov 02 2020 · 0 comments
Instructions
Test suite
Solution

A Pythagorean triplet is a set of three natural numbers, {a, b, c}, for which,

a**2 + b**2 = c**2

and such that,

a < b < c

For example,

3**2 + 4**2 = 9 + 16 = 25 = 5**2.

Given an input integer N, find all Pythagorean triplets for which a + b + c = N.

For example, with N = 1000, there is exactly one Pythagorean triplet for which a + b + c = 1000: {200, 375, 425}.

## Setup

Go through the setup instructions for Java to install the necessary dependencies:

https://exercism.io/tracks/java/installation

# Running the tests

You can run all the tests for an exercise by entering the following in your terminal:

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by removing the @Ignore("Remove to run test") annotation.

## Source

Problem 9 at Project Euler http://projecteuler.net/problem=9

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### PythagoreanTripletTest.java

import java.util.Arrays;
import java.util.List;
import java.util.Collections;
import static org.junit.Assert.assertEquals;
import org.junit.Test;
import org.junit.Ignore;

public class PythagoreanTripletTest {

@Test
public void tripletsWhoseSumIs12() {
List<PythagoreanTriplet> actual
= PythagoreanTriplet
.makeTripletsList()
.withFactorsLessThanOrEqualTo(12)
.thatSumTo(12)
.build();
List<PythagoreanTriplet> expected
= Collections.singletonList(new PythagoreanTriplet(3, 4, 5));
assertEquals(expected, actual);
}

@Ignore("Remove to run test")
@Test
public void tripletsWhoseSumIs108() {
List<PythagoreanTriplet> actual
= PythagoreanTriplet
.makeTripletsList()
.withFactorsLessThanOrEqualTo(108)
.thatSumTo(108)
.build();
List<PythagoreanTriplet> expected
= Collections.singletonList(new PythagoreanTriplet(27, 36, 45));
assertEquals(expected, actual);
}

@Ignore("Remove to run test")
@Test
public void tripletsWhoseSumIs1000() {
List<PythagoreanTriplet> actual
= PythagoreanTriplet
.makeTripletsList()
.withFactorsLessThanOrEqualTo(1000)
.thatSumTo(1000)
.build();
List<PythagoreanTriplet> expected
= Collections.singletonList(new PythagoreanTriplet(200, 375, 425));
assertEquals(expected, actual);
}

@Ignore("Remove to run test")
@Test
public void tripletsWhoseSumIs1001() {
List<PythagoreanTriplet> actual
= PythagoreanTriplet
.makeTripletsList()
.withFactorsLessThanOrEqualTo(1001)
.thatSumTo(1001)
.build();
List<PythagoreanTriplet> expected = Collections.emptyList();
assertEquals(expected, actual);
}

@Ignore("Remove to run test")
@Test
public void tripletsWhoseSumIs90() {
List<PythagoreanTriplet> actual
= PythagoreanTriplet
.makeTripletsList()
.withFactorsLessThanOrEqualTo(90)
.thatSumTo(90)
.build();
List<PythagoreanTriplet> expected
= Arrays.asList(
new PythagoreanTriplet(9, 40, 41),
new PythagoreanTriplet(15, 36, 39));
assertEquals(expected, actual);
}

@Ignore("Remove to run test")
@Test
public void tripletsWhoseSumIs840() {
List<PythagoreanTriplet> actual
= PythagoreanTriplet
.makeTripletsList()
.withFactorsLessThanOrEqualTo(840)
.thatSumTo(840)
.build();
List<PythagoreanTriplet> expected
= Arrays.asList(
new PythagoreanTriplet(40, 399, 401),
new PythagoreanTriplet(56, 390, 394),
new PythagoreanTriplet(105, 360, 375),
new PythagoreanTriplet(120, 350, 370),
new PythagoreanTriplet(140, 336, 364),
new PythagoreanTriplet(168, 315, 357),
new PythagoreanTriplet(210, 280, 350),
new PythagoreanTriplet(240, 252, 348));
assertEquals(expected, actual);
}

@Ignore("Remove to run test")
@Test
public void tripletsWhoseSumIs30000() {
List<PythagoreanTriplet> actual
= PythagoreanTriplet
.makeTripletsList()
.withFactorsLessThanOrEqualTo(30000)
.thatSumTo(30000)
.build();
List<PythagoreanTriplet> expected
= Arrays.asList(
new PythagoreanTriplet(1200, 14375, 14425),
new PythagoreanTriplet(1875, 14000, 14125),
new PythagoreanTriplet(5000, 12000, 13000),
new PythagoreanTriplet(6000, 11250, 12750),
new PythagoreanTriplet(7500, 10000, 12500));
assertEquals(expected, actual);
}

}
import java.util.List;
import java.util.ArrayList;
import java.lang.Math;

class PythagoreanTriplet{
private int a;
private int b;
private int c;

PythagoreanTriplet(int a, int b, int c){
this.a = a;
this.b = b;
this.c = c;
}

public static Builder makeTripletsList(){
return new Builder();
}

public boolean equals(Object otherObject){
PythagoreanTriplet other = (PythagoreanTriplet)otherObject;
return this.a == other.a && this.b == other.b && this.c == other.c;
}
}

class Builder{
private int sum;
private int factor;
private List<PythagoreanTriplet> list;

Builder(){
this.list = new ArrayList<PythagoreanTriplet>();
}

public Builder withFactorsLessThanOrEqualTo(int factor){
this.factor = factor;
return this;
}

public Builder thatSumTo(int sum){
this.sum = sum;
return this;
}

public List<PythagoreanTriplet> build(){
int a = 1;
int b;
int c;

while(a < this.sum  && a <= this.factor){
b = a + 1;

while(a+b < this.sum && b < this.factor){
c = this.sum - (a+b);

if(c <= factor && Math.pow(a,2) + Math.pow(b,2) == Math.pow(c,2)){
break;
}

b++;
}

a++;
}

return list;
}
}