package main

type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func main() {

}
func inorderTraversal(root *TreeNode) []int {
	if root == nil {
		return []int{}
	}
	var res []int
	leftnode := inorderTraversal(root.Left)
	rightnode := inorderTraversal(root.Right)
	res = append(res, leftnode...)
	res = append(res, root.Val)
	res = append(res, rightnode...)

	return res
}