getNearbyWords.swift

getNearbyWords.swift

//: Playground - noun: a place where people can play

import UIKit

// https://www.facebook.com/video.php?v=10152735777427200&set=vb.9445547199&type=2&theater
var str = "Hello, playground"

func getNearbyChars(ch: String) -> Set<String> {
    switch ch {
    case "g": return Set(["g","h","f"])
    case "i": return Set(["i","o","k"])
    default: return Set()
    }
}

func isWord(str: String) -> Bool {
    return ["hi", "go"].indexOf(str) != nil
}

func getNearbyWords(word: String) -> Set<String> {
    // "gi" -> [{g,h,f}, {i,o,k}]
    let sets = word.characters.map { getNearbyChars(String($0)) }
    return Set(permutation(sets).filter { isWord($0) })
}

func permutation(sets: [Set<String>]) -> [String] {
    guard let set = sets.first else { return [""] }
    return set.flatMap { ch in
        return permutation(Array(sets[1..<sets.count])).map { ch + $0 }
    }
}

getNearbyWords("gi")