Swift Merge Sort

myMergeSort.swift

let numbers = [9,29, 83, 19, 48, 65, 25, 30, 18, 1, 15, 84, 72, 63, 71]

func splitToSublists(list: Int[]) -> (Int[], Int[]) {
    assert(list.count > 1, "List size must be greater than 1 before split")
    let midIndex = (list.count / 2) as Int
    var leftSublist: Int[] = Array(list[0..midIndex])
    var rightSublist: Int[] = Array(list[midIndex..(list.count)])
    
    return (leftSublist, rightSublist)
}

func merge(left: Int[], right: Int[]) -> Int[] {
    var result: Int[] = Int[]()
    var list1 = left
    var list2 = right
    while(list1.count > 0 && list2.count > 0)
    {
        if list1[0] <= list2[0] {
            result += list1[0]
            list1 = Array(list1[1..(list1.count)])
        }
        else
        {
            result += list2[0]
            list2 = Array(list2[1..(list2.count)])
        }
    }
    if list1.count > 0 {
        result += list1
    }
    if list2.count > 0 {
        result += list2
    }
    return result
}

func myMergeSort(list: Int[]) -> Int[] {
    if list.count > 1 {
        var (leftSublist, rightSublist) = splitToSublists(list)
        leftSublist = myMergeSort(leftSublist)
        rightSublist = myMergeSort(rightSublist)
        
        return merge(leftSublist, rightSublist)
    }
    else
    {
        return list
    }
}

var sorted = myMergeSort(numbers)
println(sorted)
// prints "[1, 9, 15, 18, 19, 25, 29, 30, 48, 63, 65, 71, 72, 83, 84]"