题目：

题解：

type Codec struct{}func Constructor() (_ Codec) { return }func (Codec) serialize(root *TreeNode) string {arr := []string{}var postOrder func(*TreeNode)postOrder = func(node *TreeNode) {if node == nil {return}postOrder(node.Left)postOrder(node.Right)arr = append(arr, strconv.Itoa(node.Val))}postOrder(root)return strings.Join(arr, " ")
}func (Codec) deserialize(data string) *TreeNode {if data == "" {return nil}arr := strings.Split(data, " ")var construct func(int, int) *TreeNodeconstruct = func(lower, upper int) *TreeNode {if len(arr) == 0 {return nil}val, _ := strconv.Atoi(arr[len(arr)-1])if val < lower || val > upper {return nil}arr = arr[:len(arr)-1]return &TreeNode{Val: val, Right: construct(val, upper), Left: construct(lower, val)}}return construct(math.MinInt32, math.MaxInt32)
}