Exercises.swift

func permutations(input:String, builder: String = "") {
    var array = input.characters.map { $0 }
    var length = input.characters.count
    if length == 0 { print(builder) }
    for i in 0 ..< length {
        var lhs = String(array[0 ..< i])
        var rhs = String(array[i+1 ..< length])
        permutations(input: "\(lhs)\(rhs)", builder: builder + String(array[i]))
    }
}

func pyramid(range : Int) {
    let p = 1...range
    var strings = ""
    var ntype = range
    for p in 1...range {
        strings = "#\(strings)"
        var spaces = ""
        for n in 1...ntype {
          if n == 1 { spaces = "\(spaces)" } else { spaces = " \(spaces)" }
        }
        ntype -= 1
        if p == range - 1 { print("\(spaces)\(strings)") } else { print("\(spaces)\(strings)") }
    }
}

pyramid(range: n)

func reverseString(string:String) {
    var stingArray = string.components(separatedBy: " ")
    var newString = ""
    stingArray.forEach {
        newString = "\($0) \(newString)"
    }
    print(newString)
}

func isPrime(num:Int) -> Bool {
    guard num % 2 != 0 else { return false }
    for i in 2 ..< num {
        if num % i == 0 { return false }
    }
    return true
}

func factorial(N:Int) -> Int {
    var intVal = N
    if intVal == 0 {
        return 1
    } else {
        return intVal * factorial(N: intVal - 1)
    }
}

print(factorial(N: 6))
isPrime(num: 27)
reverseString(string: "Hello dear")