gistfile1.txt

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

import Cocoa

func f1(x : Int) -> Int? {
    return (x == 3) ? 1 : 3
}

func f2(x : Int) -> Int? {
    if x < 0 || x > 3 {return nil}
    return [3, 0, 1, 0][x - 1]
}

func f3(var x: Int) -> Int? {
    return x ^ (1 << 1)
}

func f4(x : Int) -> Int? {
    if ((x != 3) && (x != 1)) {return nil}
    let s = " 3 1"
    let index = advance(s.startIndex, x)
    return (s.substringFromIndex(index) as NSString).integerValue
}

func f5(x : Int) -> Int? {
    return [1:3, 3:1][x % 4]
}

func f6(x : Int) -> Int? {
    return Int(atan(pow(0.0, -(1.0 - Double(x))))) * 2 + 1
}

func f7(x : Int) -> Int? {
    return lrint(asin(Double((x - 1) / 2))) + 1
}

func f8(x : Int) -> Int? {
    if let i = first("\(x)".utf16) {
        return Int(sqrt(fmod(Double(i), 10.0)))
    }
    return nil
}

func f9(x : Int) -> Int? {
    return 4 - x
}

func fa(x : Int) -> Int? {
    var count = -1
    for i in 0...1 {
        count += (x & 1 << i) != 0 ? 1 : 0
    }
    
    return Int(cos(Double(count) * Double(M_PI))) + 2
}

func fb(x: Int) -> Int? {
    var set = [1, 3] as Set<Int>
    set.remove(x)
    let y = set.removeFirst()
    return isEmpty(set) ? y : nil
}

func fc(x:Int)->Int{
    typealias f = ()->Int
    var funcs = [Int : f]()
    funcs[1] = {3}
    funcs[3] = {1}
    
    return funcs[x]!()
}