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artemkorsakov's solution

to Pythagorean Triplet in the Go Track

Published at Feb 26 2019 · 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

For example,

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

There exists exactly one Pythagorean triplet for which a + b + c = 1000.

Find the product a * b * c.

Running the tests

To run the tests run the command go test from within the exercise directory.

If the test suite contains benchmarks, you can run these with the --bench and --benchmem flags:

go test -v --bench . --benchmem

Keep in mind that each reviewer will run benchmarks on a different machine, with different specs, so the results from these benchmark tests may vary.

Further information

For more detailed information about the Go track, including how to get help if you're having trouble, please visit the exercism.io Go language page.

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.

pythagorean_triplet_test.go

package pythagorean

// Use this type definition,
//
//    type Triplet [3]int
//
// and implement two functions,
//
//    Range(min, max int) []Triplet
//    Sum(p int) []Triplet
//
// Range returns a list of all Pythagorean triplets with sides in the
// range min to max inclusive.
//
// Sum returns a list of all Pythagorean triplets where the sum a+b+c
// (the perimeter) is equal to p.
//
// The three elements of each returned triplet must be in order,
// t[0] <= t[1] <= t[2], and the list of triplets must be in lexicographic
// order.

import (
	"reflect"
	"testing"
)

var rangeTests = []struct {
	min, max int
	ts       []Triplet
}{
	{1, 10, []Triplet{{3, 4, 5}, {6, 8, 10}}},
	{11, 20, []Triplet{{12, 16, 20}}},
}

func TestRange(t *testing.T) {
	for _, test := range rangeTests {
		ts := Range(test.min, test.max)
		if !reflect.DeepEqual(ts, test.ts) {
			t.Fatalf("Range(%d, %d) = %v, want %v",
				test.min, test.max, ts, test.ts)
		}
	}
}

var sumTests = []struct {
	sum int
	ts  []Triplet
}{
	{180, []Triplet{{18, 80, 82}, {30, 72, 78}, {45, 60, 75}}},
	{1000, []Triplet{{200, 375, 425}}},
}

func TestSum(t *testing.T) {
	for _, test := range sumTests {
		ts := Sum(test.sum)
		if !reflect.DeepEqual(ts, test.ts) {
			t.Fatalf("Sum(%d) = %v, want %v",
				test.sum, ts, test.ts)
		}
	}
}

func BenchmarkRange(b *testing.B) {
	for i := 0; i < b.N; i++ {
		Range(1, 100)
	}
}

func BenchmarkSum(b *testing.B) {
	for i := 0; i < b.N; i++ {
		Sum(1000)
	}
}
package pythagorean

// Triplet is a Pythagorean triplet.
// A Pythagorean triplet is a set of three natural numbers, {a, b, c}, for which, a**2 + b**2 = c**2.
type Triplet [3]int

// Range returns a list of all Pythagorean triplets with sides in the
// range min to max inclusive.
func Range(min int, max int) []Triplet {
	result := make([]Triplet, 0)
	for a := min; a < max-1; a++ {
		for b := a + 1; b < max; b++ {
			for c := b + 1; c < max+1; c++ {
				if a*a+b*b == c*c {
					result = append(result, [3]int{a, b, c})
				}
			}
		}
	}

	return result
}

// Sum returns a list of all Pythagorean triplets where the sum a+b+c
// (the perimeter) is equal to p.
// a less b less c   therefore   a less sum / 3; b less (sum - 1) / 2
func Sum(sum int) []Triplet {
	result := make([]Triplet, 0)
	for a := 1; a < sum/3; a++ {
		for b := a + 1; b < (sum-1)/2; b++ {
			c := sum - a - b
			if a*a+b*b == c*c {
				result = append(result, [3]int{a, b, c})
			}
		}
	}

	return result
}

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