在Swift 3中过滤复杂的嵌套数组

Question

我有一个像这样的复杂数组（树）：

[0] code = "pc1"
    children
      [0] code = "gc1"
          children
              [0] code = "cc1"
                  children = nil
              [1] code = "cc2"
                  children = nil
      [1] code = "gc2"
          children = nil
[1] code = "pc2"
    children = nil

我想要的是搜索没有孩子的任何节点。如果找到任何儿童笔记，我想保持层次结构。例如，搜索“2”将返回：

[0] code = "pc1"
    children
      [0] code = "gc1"
          children
              [0] code = "cc2"
                  children = nil
      [1] code = "gc2"
          children = nil
[1] code = "pc2"
    children = nil

搜索“p”将返回：

[0] code = "pc1"
    children
[1] code = "pc2"
    children = nil

我试了好久。但未能找到解决方案。任何的想法？感谢。

于2017年8月27日编辑：

这是我的树类：

class Node {

  var parentCode: String = ""

  weak var parent: Node?
  lazy var children = [Node]()

  init() {}

  func add(node: Node) {
    children.append(code)
    code.parent = self
  }

如果我想搜索 o 字母，那将是结果。