（Python）从二叉树交替输入？

Question

So I've just begun the meat and potatoes of my degree and I'm learning Python. One of our assignments this week was to use a binary tree and add guests, allowing the tree to alternate left and right, then print the names of left and right aisle guests.

Our professor gave us some sample code to work with, and I made a few changes to have it do what I wanted to do with it. Here's what I have:

guestnumber = 0
class Node:
    def __init__(self):
        self.left = None
        self.right = None
        self.data = list()

def guestadd(root, Guest):
    if Guest <= root.data[0]:
        if root.left == None:
            root.left = Node()
            root.left.data.append(Guest)
        else:
            guestadd(root.left, Guest)
    else:
        if Guest >= root.data[0]:
            if root.right == None:
                root.right = Node()
                root.right.data.append(Guest)
            else:
                guestadd(root.right, Guest)

def printlist(root):
    if root == None:
        return
    print(root.data)
    printlist(root.left)
    printlist(root.right)

print("Enter guest names for seating arrangements. (Max = 50)")
guestnumber = int(input("How many guests are attending?"))
root = Node()
root.data.append("Guest")
for i in range (0,guestnumber):
    guestadd (root, input("Name:"))

print("Left Aisle:")
printlist(root.left)
print("Right Aisle:")
printlist(root.right)

At first glance, everything works as intended, but I noticed I was given inconsistent results where it didn't split the names evenly. After sleeping on it, I did some more troubleshooting and discovered that, no matter what order I put the data in, it would always put 0-9, AG, and a handful of special characters on the left node, and HZ, az, and another handful of special characters on the right side.

I've already handed in what I have, along with several screenshots of my discoveries, so I'm sure I'll be given full credit, given that's it's an introductory course. But it's bugging me that I can't get get it to do what I want consistently.

My best guess is that it has something to do with where the characters lie on an ASCII chart. Everything from 0-71 was on the left, and 72-127 on the right. How would I go about getting my program to treat the strings as just that and not thinking of it in ASCII?

NOTE: If I was given this task to separate guests, I wouldn't use a tree. I'd probably use something that just adds names to an list, then use a [::2] and [1::2] slice to alternate sides. However, since the assignment was to learn how to use a binary tree, I wanted to stay with the constraints of the lesson

Answer 1

You have nothing in your code about alternating left and right. You've built a binary search tree with "Guest" at the root. Anyone whose name comes before "Guest" in Unicode-lexicographic order goes on the left, and anyone whose name comes after "Guest" in Unicode-lexicographic order goes on the right.