Collatz Sequence Longest Chain Number

pattern.playground

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

import UIKit

var million = 1000000

var bestLength = 0
var bestNumber = 0
var number = 0

for i in 2 ... million {
    var length = 1
    number = i
    
    while number != 1 {
        number = number % 2 == 0 ? number / 2 : number * 3 + 1
        length++
    }
    
    if length > bestLength {
        bestLength = length
        bestNumber = i
    }
}

// Answer is 837799
println("Best Number is \(bestNumber) with Lenght \(bestLength)")