ROT13.swift

//: ROT13 Swift 1.2 - by jgallagher

var rot13key = [Character:Character]()

let uppercase = Array("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
let lowercase = Array("abcdefghijklmnopqrstuvwxyz")

for var i = 0; i < 26; i++ {
    rot13key[uppercase[i]] = uppercase[(i + 13) % 26]
    rot13key[lowercase[i]] = lowercase[(i + 13) % 26]
}

func rot13(s: String) -> String {
    return String(map(s, { rot13key[$0] ?? $0 }))
}

let encoded = rot13("Secret Message")
let decoded = rot13(encoded)

print("secret message encoded \(encoded)")
print("secret message decoded \(decoded)")