Merge pull request #352 from runnerdave/letter-frequency

Letter frequency

03_letters/runnerdave/main.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+var out io.Writer = os.Stdout
+
+func letters(s string) map[rune]int {
+	stats := make(map[rune]int)
+	for _, char := range s {
+		stats[char]++
+	}
+	return stats
+}
+
+func sortLetters(m map[rune]int) []string {
+	keys := make([]rune, 0)
+	for k := range m {
+		keys = append(keys, k)
+	}
+	sorted(keys)
+	sortedArray := make([]string, len(keys))
+	for i, k := range keys {
+		sortedArray[i] = fmt.Sprintf("%s:%s", string(k), strconv.Itoa(m[k]))
+	}
+	return sortedArray
+}
+
+func main() {
+	fmt.Fprintln(out, strings.Join(sortLetters(letters("aba")), "\n"))
+}
+
+type runeSlice []rune
+
+func (p runeSlice) Len() int           { return len(p) }
+func (p runeSlice) Less(i, j int) bool { return p[i] < p[j] }
+func (p runeSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+func sorted(runes []rune) string {
+	sort.Sort(runeSlice(runes))
+	return string(runes)
+}

03_letters/runnerdave/main_test.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"bytes"
+	"reflect"
+	"strconv"
+	"testing"
+)
+
+func TestMainOutput(t *testing.T) {
+	var buf bytes.Buffer
+	out = &buf
+
+	main()
+
+	expected := strconv.Quote(`a:2
+b:1
+`)
+	actual := strconv.Quote(buf.String())
+	t.Logf("expected:%s", expected)
+	t.Logf("actual:%s", actual)
+
+	if expected != actual {
+		t.Errorf("Unexpected output in main()")
+	}
+}
+
+func TestLetters(t *testing.T) {
+	tables := []struct {
+		n string
+		x map[rune]int
+	}{
+		{"aaa", map[rune]int{'a': 3}},
+		{"bbbb", map[rune]int{'b': 4}},
+		{"B", map[rune]int{'B': 1}},
+		{"bbbB", map[rune]int{'b': 3, 'B': 1}},
+		{"bbbBCcccc", map[rune]int{'b': 3, 'B': 1, 'C': 1, 'c': 4}},
+		{"bbbBCbbbb", map[rune]int{'b': 7, 'B': 1, 'C': 1}},
+		{"", map[rune]int{}},
+	}
+	for _, table := range tables {
+		result := letters(table.n)
+		if !reflect.DeepEqual(result, table.x) {
+			t.Errorf("Function Letters for (%s) was incorrect, got: %v, want: %v.", table.n, result, table.x)
+		}
+	}
+}
+
+func TestSortingLetters(t *testing.T) {
+	tables := []struct {
+		x map[rune]int
+		n []string
+	}{
+		{map[rune]int{'a': 1, 'b': 3}, []string{"a:1", "b:3"}},
+		{map[rune]int{'c': 1, 'b': 3}, []string{"b:3", "c:1"}},
+		{map[rune]int{'m': 1, 'b': 3, 'd': 5}, []string{"b:3", "d:5", "m:1"}},
+		{map[rune]int{'a': 1, 'A': 3}, []string{"A:3", "a:1"}},
+		{map[rune]int{'n': 1, 'N': 3}, []string{"N:3", "n:1"}},
+		{map[rune]int{'n': 0, 'N': 3}, []string{"N:3", "n:0"}},
+		{map[rune]int{}, []string{}},
+	}
+
+	for _, table := range tables {
+		sorted := sortLetters(table.x)
+		if !reflect.DeepEqual(sorted, table.n) {
+			t.Errorf("Sorting of (%v) was incorrect, got: %v, want: %v.", table.x, sorted, table.n)
+		}
+	}
+}