Tree

In order traversal

# Iterative using visited attribute

def in_order_ite
    s = Stack.new
    s.push root

    until s.empty?
      c = s.last

      if c.left && !c.left.visited
        s.push c.left
      else
        c = s.pop
        c.visit
        if c.right
          s.push c.right
        end
      end

    end
  end
 end
 
 #Iterative without uusing visited attribute
  def in_order_ite
    s = Stack.new
    current = root
    done = false

    until done
      if current
        s.push current
        current = current.left
      else
        if !s.empty?
          current = s.pop
          current.visit
          
          current = current.right
        else
          done = true
        end
      end
    end

  end