From 15b34b4ce1eb481905d5a4fb7b62bab31e24039b Mon Sep 17 00:00:00 2001
From: Erocs <github@erocs.org>
Date: Wed, 11 Jan 2017 22:57:29 -0800
Subject: [PATCH] [Go] Challenge 6

---
 challenge_6/go/erocs/README.md                | 17 ++++
 .../go/erocs/src/challenge6/challenge6.go     | 52 ++++++++++++
 .../erocs/src/challenge6/challenge6_test.go   | 84 +++++++++++++++++++
 3 files changed, 153 insertions(+)
 create mode 100644 challenge_6/go/erocs/README.md
 create mode 100644 challenge_6/go/erocs/src/challenge6/challenge6.go
 create mode 100644 challenge_6/go/erocs/src/challenge6/challenge6_test.go

diff --git a/challenge_6/go/erocs/README.md b/challenge_6/go/erocs/README.md
new file mode 100644
index 000000000..4c95f8425
--- /dev/null
+++ b/challenge_6/go/erocs/README.md
@@ -0,0 +1,17 @@
+# Challenge 6: Determine Ranges
+
+## 1. Solution Description
+
+Since the input slice will always be sorted, this code creates a new _Range_
+using the first number. Subsequent numbers that are a single integer larger then
+the previous will update the _Range_'s End value to match. When the end of the
+input slice or a non-consecutive value is encountered, the current _Range_ will
+be appended to the result slice and a new _Range_ will be created using the
+value. Single value _Range_s (ex. 1->1) are omitted from the result slice.
+
+## 2. Running Tests
+
+In bash in this directory:
+
+    export GOPATH=`pwd`
+    go test challenge6
diff --git a/challenge_6/go/erocs/src/challenge6/challenge6.go b/challenge_6/go/erocs/src/challenge6/challenge6.go
new file mode 100644
index 000000000..16e73f28f
--- /dev/null
+++ b/challenge_6/go/erocs/src/challenge6/challenge6.go
@@ -0,0 +1,52 @@
+package challenge6
+
+import "fmt"
+
+// Tracks the start and end points of a range of consecutive integers.
+type Range struct {
+	Start int
+	End   int
+}
+
+// Creates a new range with Start and End equalling n.
+func NewRange(n int) Range {
+	return Range{Start: n, End: n}
+}
+
+func (r *Range) String() string {
+	return fmt.Sprintf("%d->%d", r.Start, r.End)
+}
+
+type RangeSlice []Range
+
+func (rs RangeSlice) ToStrings() []string {
+	strs := make([]string, 0, len(rs))
+	for _, r := range rs {
+		strs = append(strs, r.String())
+	}
+	return strs
+}
+
+// Determines all ranges of consecutive values within the sorted input slice,
+// ints. Resulting ranges consist of two or more values.
+func FindRanges(ints []int) RangeSlice {
+	if len(ints) <= 0 {
+		return RangeSlice([]Range{})
+	}
+	ranges := make([]Range, 0, len(ints)/2)
+	r := NewRange(ints[0])
+	for _, i := range ints[1:] {
+		if r.End+1 == i {
+			r.End = i
+		} else {
+			if r.Start != r.End {
+				ranges = append(ranges, r)
+			}
+			r = NewRange(i)
+		}
+	}
+	if r.Start != r.End {
+		ranges = append(ranges, r)
+	}
+	return RangeSlice(ranges)
+}
diff --git a/challenge_6/go/erocs/src/challenge6/challenge6_test.go b/challenge_6/go/erocs/src/challenge6/challenge6_test.go
new file mode 100644
index 000000000..4ad5fc99e
--- /dev/null
+++ b/challenge_6/go/erocs/src/challenge6/challenge6_test.go
@@ -0,0 +1,84 @@
+package challenge6
+
+import (
+	"strings"
+	"testing"
+)
+
+// Call challenge6.FindRanges() on _ints_ and concatenate the ranges into a
+// single string for comparison testing.
+func FR(ints []int) string {
+	return strings.Join(FindRanges(ints).ToStrings(), " ")
+}
+
+func TestEmpty(t *testing.T) {
+	ex := ""
+	r := FR([]int{})
+	if r != ex {
+		t.Error("Mismatch, expected:", ex, "received:", r)
+	}
+}
+
+func TestSingleton(t *testing.T) {
+	ex := ""
+	r := FR([]int{1})
+	if r != ex {
+		t.Error("Mismatch, expected:", ex, "received:", r)
+	}
+}
+
+func TestSimpleRange(t *testing.T) {
+	ex := "1->2"
+	r := FR([]int{1, 2})
+	if r != ex {
+		t.Error("Mismatch, expected:", ex, "received:", r)
+	}
+}
+
+func TestNegativeRange(t *testing.T) {
+	ex := "-2->-1"
+	r := FR([]int{-2, -1})
+	if r != ex {
+		t.Error("Mismatch, expected:", ex, "received:", r)
+	}
+}
+
+func TestLongRange(t *testing.T) {
+	ex := "1->20000"
+	c := 20000
+	ints := make([]int, 0, c)
+	for i := 1; i <= c; i++ {
+		ints = append(ints, i)
+	}
+	r := FR(ints)
+	if r != ex {
+		t.Error("Mismatch, expected:", ex, "received:", r)
+	}
+}
+
+// TestTwoRanges
+func TestRR(t *testing.T) {
+	ex := "10->12 14->16"
+	r := FR([]int{10, 11, 12, 14, 15, 16})
+	if r != ex {
+		t.Error("Mismatch, expected:", ex, "received:", r)
+	}
+}
+
+// TestSingletonRangeSingleton
+func TestSRS(t *testing.T) {
+	ex := "4->6"
+	r := FR([]int{2, 4, 5, 6, 8})
+	if r != ex {
+		t.Error("Mismatch, expected:", ex, "received:", r)
+	}
+}
+
+// TestRangeSingletonRange
+func TestRSR(t *testing.T) {
+	ex := "1->3 7->9"
+	r := FR([]int{1, 2, 3, 5, 7, 8, 9})
+	if r != ex {
+		t.Error("Mismatch, expected:", ex, "received:", r)
+	}
+}