golang力扣leetcode 297.二叉树的序列化与反序列化

1.序列化：前序遍历，根左右
2.反序列化：递归，根左右

type TreeNode struct {
  Val   int
  Left  *TreeNode
  Right *TreeNode
}
type Codec struct{}
func Constructor() (_ Codec) {
  return
}
func (Codec) serialize(root *TreeNode) string {
  ss := make([]string, 0)
  var dfs func(*TreeNode)
  dfs = func(root *TreeNode) {
    if root == nil {
      ss = append(ss, "null")
      return
    }
    ss = append(ss, strconv.Itoa(root.Val))
    dfs(root.Left)
    dfs(root.Right)
  }
  dfs(root)
  return strings.Join(ss, ",")
}
func (Codec) deserialize(data string) *TreeNode {
  ss := strings.Split(data, ",")
  var build func() *TreeNode
  build = func() *TreeNode {
    if ss[0] == "null" {
      ss = ss[1:]
      return nil
    }
    val, _ := strconv.Atoi(ss[0])
    ss = ss[1:]
    return &TreeNode{val, build(), build()}
  }
  return build()
}