Interview. Binary trees

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

// example of max node
// assume that all nodes' values are > 0
func dfs(root *TreeNode)int{
    if root == nil{
      // neutral for result output
      return 0
    }

    // doing for both subtrees
    leftMax:=dfs(root.Left)
    rightMax:=dfs(root.Max)

    // CORE LOGIC GOES HERE
    result:=Max(root.Val, leftMax, rightMax)
    // CORE LOGIC ENDS HERE

    return result
}

// example of max node
// assume that all nodes' values are > 0
func dfs(root *TreeNode)int{
    max := 0
    current  := root
    stack := []*TreeNode{}

    for current !=nil || len(stack)!=0{
      // navigating to last Left leaf node for current parent
      // and pushing them to stack to process later
      for current !=nil{
        stack = append(stack, current)
        current = current.Left
      }

      //poping element from stack
      current = stack[len(stack)-1]
      stack = stack[:len(stack)-1]

      // CORE LOGIC GOES HERE
      // we have an element to work with
      max = Max(max, current.Val)
      // CORE LOGIC ENDS HERE

      // pointing to right node now
      // if it doesn't exist we will pick next from stack, or exit the loop
      current = current.Right
    }
    return max
}

// example of max node
// assume that all nodes' values are > 0
func dfs(root *TreeNode)int{
    max := 0
    current  := root
    stack := []*TreeNode{}

    for current !=nil || len(stack)!=0{
      // navigating to last Left leaf node for current parent
      // and pushing them to stack to process later
      for current !=nil{
        stack = append(stack, current)
        current = current.Left
      }

      //poping element from stack
      current = stack[len(stack)-1]
      stack = stack[:len(stack)-1]

      // CORE LOGIC GOES HERE
      // we have an element to work with
      max = Max(max, current.Val)
      // CORE LOGIC ENDS HERE

      // pointing to right node now
      // if it doesn't exist we will pick next from stack, or exit the loop
      current = current.Right
    }
    return max
}

if stacks = removeFromHighest(stacks); stacks == nil {
            return 0
}