Solution: ROT13

---

examples/rot13/rot13.go

package main

import (
    "fmt"
    "strings"
)

func main() {
    original := "abcdefghijklmnopqrstyvwxyz ABCQRS !?¡ñ"
    //original = "Hello World!"
    fmt.Println(len(original))
    encrypted := rot13(original)
    decrypted := rot13(encrypted)

    fmt.Println(original)
    fmt.Println(encrypted)
    fmt.Println(decrypted)
    fmt.Println(original == decrypted)
}

func rot13(input string) string {
    result := make([]string, 0, len(input))
    for _, chr := range input {
        if 'a' <= chr && chr <= 'z' {
            chr = ((chr - 'a' + 13) % 26) + 'a'
        }
        if 'A' <= chr && chr <= 'Z' {
            chr = ((chr - 'A' + 13) % 26) + 'A'
        }
        result = append(result, string(chr))
    }
    output := strings.Join(result, "")
    return output
}