Merge pull request #67 from exercism/pythagorean-triplet

add exercise pythagorean triplet

config.json

@@ -16,6 +16,7 @@
     "parallel-letter-frequency",
     "hamming",
     "sum-of-multiples",
+    "pythagorean-triplet",
     "luhn",
     "largest-series-product",
     "sieve",

pythagorean-triplet/example.go

@@ -0,0 +1,32 @@
+package pythagorean
+
+type Triplet [3]int
+
+func pyth(a, b, c int) bool {
+	return a*a+b*b == c*c
+}
+
+func Range(min, max int) (ts []Triplet) {
+	for a := min; a <= max; a++ {
+		for b := a; b <= max; b++ {
+			for c := b; c <= max; c++ {
+				if pyth(a, b, c) {
+					ts = append(ts, Triplet{a, b, c})
+				}
+			}
+		}
+	}
+	return
+}
+
+func Sum(sum int) (ts []Triplet) {
+	max := sum / 2
+	for a := 1; a <= max; a++ {
+		for b := a; b <= max; b++ {
+			if c := sum - a - b; pyth(a, b, c) {
+				ts = append(ts, Triplet{a, b, c})
+			}
+		}
+	}
+	return
+}

pythagorean-triplet/pythagorean_triplet_test.go

@@ -0,0 +1,73 @@
+package pythagorean
+
+// Use this type defintion,
+//
+//    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)
+	}
+}