Initial Commit

go/pythagorean-triplet/README.md

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+# Pythagorean Triplet
+
+There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.
+
+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.
+```
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://help.exercism.io/getting-started-with-go.html).
+
+## Source
+
+Problem 9 at Project Euler [view source](http://projecteuler.net/problem=9)

go/pythagorean-triplet/pythagorean.go

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+package pythagorean
+
+import "math"
+
+// Triplet just holds three ints
+type Triplet struct {
+	a, b, c int
+}
+
+// Range finds all pythagorean triplets
+// from min to max
+func Range(min, max int) []Triplet {
+	var ret []Triplet
+	for a := min; a <= max; a++ {
+		for b := a + 1; b <= max; b++ {
+			cSq := float64(a*a + b*b)
+			c := int(math.Sqrt(cSq))
+			if c >= min && c <= max && isTriplet(a, b, c) {
+				ret = append(ret, Triplet{a, b, c})
+			}
+		}
+	}
+	return ret
+}
+
+// Sum finds all triplets that sum up to total
+func Sum(total int) []Triplet {
+	var ret []Triplet
+
+	// No side of a triangle can be over 1/2 of the total
+	for a := 1; a <= (total / 2); a++ {
+		for b := a; b <= (total / 2); b++ {
+			c := total - a - b
+			if isTriplet(a, b, c) {
+				ret = append(ret, Triplet{a, b, c})
+			}
+		}
+	}
+	return ret
+}
+
+func isTriplet(a, b, c int) bool {
+	return (a*a + b*b) == c*c
+}

go/pythagorean-triplet/pythagorean_triplet_test.go

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+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)
+	}
+}