Merge Go Work

go/atbash-cipher/README.md

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+# Atbash Cipher
+
+Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
+
+The Atbash cipher is a simple substitution cipher that relies on
+transposing all the letters in the alphabet such that the resulting
+alphabet is backwards. The first letter is replaced with the last
+letter, the second with the second-last, and so on.
+
+An Atbash cipher for the Latin alphabet would be as follows:
+
+```plain
+Plain:  abcdefghijklmnopqrstuvwxyz
+Cipher: zyxwvutsrqponmlkjihgfedcba
+```
+
+It is a very weak cipher because it only has one possible key, and it is
+a simple monoalphabetic substitution cipher. However, this may not have
+been an issue in the cipher's time.
+
+Ciphertext is written out in groups of fixed length, the traditional group size
+being 5 letters, and punctuation is excluded. This is to make it harder to guess
+things based on word boundaries.
+
+## Examples
+- Encoding `test` gives `gvhg`
+- Decoding `gvhg` gives `test`
+- Decoding `gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt` gives `The quick brown fox jumps over the lazy dog.`
+
+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://exercism.io/languages/go).
+
+## Source
+
+Wikipedia [http://en.wikipedia.org/wiki/Atbash](http://en.wikipedia.org/wiki/Atbash)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

go/atbash-cipher/atbash.go

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+package atbash
+
+import "strings"
+
+func Atbash(s string) string {
+	s = strings.ToLower(s)
+	var v []byte
+	var b, iter int
+	for i := range s {
+		sv := int(s[i])
+		switch {
+		case sv < 48:
+			continue
+		case sv >= 48 && sv <= 57:
+			b = sv
+		case sv < 109:
+			b = 110 + (109 - sv)
+		case sv == 109:
+			b = 110
+		case sv == 110:
+			b = 109
+		case sv > 110:
+			b = 109 - (sv - 110)
+		}
+		v = append(v, byte(b))
+		iter++
+		if iter == 5 {
+			v = append(v, ' ')
+			iter = 0
+		}
+	}
+	if iter == 0 {
+		return string(v)[:len(string(v))-1]
+	}
+	return string(v)
+}

go/atbash-cipher/atbash_cipher_test.go

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+package atbash
+
+import "testing"
+
+var tests = []struct {
+	expected string
+	s        string
+}{
+	{"ml", "no"},
+	{"ml", "no"},
+	{"bvh", "yes"},
+	{"lnt", "OMG"},
+	{"lnt", "O M G"},
+	{"nrmwy oldrm tob", "mindblowingly"},
+	{"gvhgr mt123 gvhgr mt", "Testing, 1 2 3, testing."},
+	{"gifgs rhurx grlm", "Truth is fiction."},
+	{"gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt", "The quick brown fox jumps over the lazy dog."},
+}
+
+func TestAtbash(t *testing.T) {
+	for _, test := range tests {
+		actual := Atbash(test.s)
+		if actual != test.expected {
+			t.Errorf("Atbash(%s): expected %s, actual %s", test.s, test.expected, actual)
+		}
+	}
+}
+
+func BenchmarkAtbash(b *testing.B) {
+	b.StopTimer()
+	for _, test := range tests {
+		b.StartTimer()
+
+		for i := 0; i < b.N; i++ {
+			Atbash(test.s)
+		}
+
+		b.StopTimer()
+	}
+}

go/atbash-cipher/cmd/main.go

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+package main
+
+import (
+	"fmt"
+
+	"../../atbash-cipher"
+)
+
+func main() {
+	fmt.Println(atbash.Atbash("mindblowingly"))
+}