题目：

题解：

type Codec struct{}

func Constructor() (_ Codec) {
    return
}

func (c Codec) serialize(root *TreeNode) string {
    if root == nil {
        return "X"
    }
    left := "(" + c.serialize(root.Left) + ")"
    right := "(" + c.serialize(root.Right) + ")"
    return left + strconv.Itoa(root.Val) + right
}

func (Codec) deserialize(data string) *TreeNode {
    var parse func() *TreeNode
    parse = func() *TreeNode {
        if data[0] == 'X' {
            data = data[1:]
            return nil
        }
        node := &TreeNode{}
        data = data[1:] // 跳过左括号
        node.Left = parse()
        data = data[1:] // 跳过右括号
        i := 0
        for data[i] == '-' || '0' <= data[i] && data[i] <= '9' {
            i++
        }
        node.Val, _ = strconv.Atoi(data[:i])
        data = data[i:]
        data = data[1:] // 跳过左括号
        node.Right = parse()
        data = data[1:] // 跳过右括号
        return node
    }
    return parse()
}