def preOrder(root):
    # it would be useful to have a stack here to keep track of the next node to visit
    # if I start going down a left child, the next node to visit would be the right child
    # I also will need to set my current pointer to the current node
    # and create a result array
    
    cur = root
    stack = []
       
    # my loop is finished when
    # cur is None - OR
    # stack is None - stack is only None at beginning or end
    
    while cur or stack:
        if cur:
            print(cur.info, end=' ')
            stack.append(cur.right)
            cur = cur.left
        else:
            cur = stack.pop()