Project Euler #6 solution code samples using Swift, Ruby, and JavaScript. Find full article here: http://mohamad.im

javascript.js

//
// Using MapReduce
//

function arrayOfNumbers(n, square) {
    return Array.apply(null, Array(n)).map(function (e, i) {
        i += 1;
        return i * (square ? i : 1);
    });
}

function difference(n) {
    var sumOfSquares = arrayOfNumbers(n, true).reduce(function (a, b) {
        return a + b;
    });

    var squareOfSum = arrayOfNumbers(n).reduce(function (a, b) {
        return a + b;
    });

    squareOfSum *= squareOfSum;
    return  squareOfSum - sumOfSquares;
}

var start = performance.now();
console.log(difference(125000));
var finish = performance.now();

console.log("MapReduce 125,000 finished in " + (finish - start) / 1000)

//
// Using while Loop
//

function diff(n) {
    var sumOfSquares = squareOfSum = 0;

    while(n) {
        sumOfSquares += n * n, squareOfSum += n, n--;
    }

    squareOfSum *= squareOfSum;
    return squareOfSum - sumOfSquares;
}

var start = performance.now();
console.log(diff(1000000000));
var finish = performance.now();

console.log("Loop 1,000,000,000 finished in " + (finish - start) / 1000)

ruby.rb

require 'benchmark'

def map_reduce(n)
  (1..n).reduce(:+)**2 - (1..n).map { |n| n**2 }.reduce(:+)
end

def enum(n)
  sumOfSquares = squareOfSum = 0
  n.downto 1 do |i|
    squareOfSum += i; sumOfSquares += i * i
  end
  (squareOfSum *= squareOfSum) - sumOfSquares
end

def while_loop(n)
  sumOfSquares = squareOfSum = 0
  while n > 0
    squareOfSum += n; sumOfSquares += n * n; n -= 1
  end
  (squareOfSum *= squareOfSum) - sumOfSquares
end

def induction(n)
  (n * (n + 1) / 2)**2 - (n * (n + 1)) * ((n * 2) + 1) / 6
end

iterations = 10_000_000
puts "Benchmarking with #{iterations} iterations"

Benchmark.bm do |bm|
  bm.report "MapReduce" do
    map_reduce(iterations)
  end

  bm.report "Enum     " do
    enum(iterations)
  end

  bm.report "Loop     " do
    while_loop(iterations)
  end

  bm.report "Induction" do
    induction(1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000)
  end
end

# Benchmarking with 10000000 iterations
#        user     system      total        real
# MapReduce  2.890000   0.030000   2.920000 (  2.928501)
# Enum       1.610000   0.010000   1.620000 (  1.611081)
# Loop       1.200000   0.000000   1.200000 (  1.201676)
# Induction  0.000000   0.000000   0.000000 (  0.000010)

swift.swift

//
// Functional approach
//

func diff(n: Int) -> Int {
    let array = [Int](1...n)

    let sumOfSquares = array.map({ $0 * $0 }).reduce(0, +)
    let sum = array.reduce(0, +)
    let squareOfSum = sum * sum

    return squareOfSum - sumOfSquares
}

//
// Using a loop
//

func loopDiff(var i: Int) -> Int {
    var sumOfSquares = 0; var squareOfSum = 0

    while i > 0 {
        sumOfSquares += i * i; squareOfSum += i; i--
    }

    squareOfSum *= squareOfSum
    return squareOfSum - sumOfSquares
}

let startTime = CFAbsoluteTimeGetCurrent()
let result = loopDiff(10000)
let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime

println("Time elapsed : \(timeElapsed) s")
println(result)