Tree serialization & deserialization

class Node {
    var children : [Node]
    var value : Int
    init(_ val: Int) {
        value = val
        children = [Node]()
    }
}
//1,-2,-3,—-4,—--5,—--6,-7
let n1 = Node(1)
let n2 = Node(2)
let n3 = Node(3)
let n4 = Node(4)
let n5 = Node(5)
let n6 = Node(6)
let n7 = Node(7)
let n8 = Node(8)

n1.children.append(n2)
n1.children.append(n3)
n1.children.append(n7)
n3.children.append(n4)
n3.children.append(n5)
n3.children.append(n6)
n5.children.append(n8)

func getTreeString(_ root: Node) -> String{
    var str = ""
    return getStr(root, &str)
}

func getStr(_ node: Node, _ prefix: inout String ) -> String{
    var res = "\(prefix)\(node.value)"
    prefix.append("-")
    for child in node.children{
        let sub = getStr(child, &prefix)
        res.append(",\(sub)")
    }
    prefix.removeLast()
    return res
}

var str = ""
let res = getTreeString(n1)
print(res)



func buildTree(_ str: String) -> Node{
    let arr = str.split(separator: ",")
    var strarr = [String]()
    for t in arr{
        strarr.append(String(t))
    }

    let root = CreatNode(strarr.removeFirst())
    getTree(&strarr, root, 2)
    return root
}



func getTree(_ arr: inout [String], _ root : Node, _ currLevel : Int){
    var res = [Node]()
    while arr.count > 0 {
        let next = arr.first!.count
        if next > currLevel{  // go to next level
            getTree(&arr, res.last!, currLevel + 1)
        }else if next == currLevel {
            let node = CreatNode(arr.removeFirst())
            res.append(node)
        }else{
            break
        }
    }
    root.children = res
}

func CreatNode(_ str: String) -> Node {
    var st = str
    while st.first! == "-"{
        st.removeFirst()
    }
    return Node(Int(st)!)
}



let node = buildTree(res)

let res2 = getTreeString(node)
print(res2)