golang力扣leetcode 94.二叉树的中序遍历

package main
type TreeNode struct {
  Val   int
  Left  *TreeNode
  Right *TreeNode
}
func inorderTraversal1(root *TreeNode) []int {
  if root == nil {
    return nil
  }
  var stack []*TreeNode
  var result []int
  for root != nil || len(stack) > 0 {
    for root != nil {
      stack = append(stack, root)
      root = root.Left
    }
    //pop
    val := stack[len(stack)-1]
    stack = stack[:len(stack)-1]
    result = append(result, val.Val)
    root = val.Right
  }
  return result
}
func inorderTraversal2(root *TreeNode) []int {
  var inorder func(root *TreeNode)
  var result []int
  inorder = func(root *TreeNode) {
    if root == nil {
      return
    }
    inorder(root.Left)
    result = append(result, root.Val)
    inorder(root.Right)
  }
  inorder(root)
  return result
}
func main() {
}