Solution to problem 1 from "5 Programming Problems, 1 Hour"

problem_1_of_5.swift

//: Problem 1
//  "Write three functions that compute the sum of the numbers in a given list using a for-loop, a while-loop, and recursion."
//  https://www.shiftedup.com/2015/05/07/five-programming-problems-every-software-engineer-should-be-able-to-solve-in-less-than-1-hour

//  Xcode 7.0, Swift 2.0

let series = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
let realSum = series.reduce(0, combine: +)


// for-loop
var forLoopSum = 0
for n in series {
    forLoopSum += n
}

assert(forLoopSum == realSum)


// while-loop
var whileLoopSum = 0
var i = 0
while i < series.count {
    whileLoopSum += series[i]
    i++
}

assert(whileLoopSum == realSum)


// recursion
func sum(var series: [Int]) -> Int {
    guard series.count > 0 else { return 0 }
    return series.removeFirst() + sum(series)
}

assert(sum(series) == realSum)