Question

I am trying to binary create a tree from a binary sequence like “100101”
then i want the tree to be created like this. (Basically 1 means go to the right and 0 means go to the left)

                                <Root node>
                                    |
                                    1
                                   /
                                  0
                                 /
                                0
                                 \
                                  1
                                 /
                                0
                                 \
                                  1

so i did it here is the code:
where the value would be the string sequence (ex value = “1001”)

def _inserto(root,value):
    for i in value:
        if root == None:
            root = BSTNode(i)
            current = root
        elif i == "1":
            if current.right is not None:
                current.right = BSTNode(i)
                current = current.right
            else:
                current.right = BSTNode(i)
                current = current.right
        elif i == "0":
            if (current.left is not None):
                current.left = BSTNode(i)
                current = current.left
            else:
                current.left =BSTNode(i)
                current = current.left
    return root

Now the problem is that if i want to input another sequence like “01”, the tree should look like this

                            <Root Node>
                                |
                                1
                               /
                              0
                             / \
                            0   1
                             \
                              1
                             /
                            0
                             \
                              1

, but i am really having a hard time, since my function is going to over-write the old tree.

Answer 1

The problem is with the code dealing with an existing node. If it is present, the code overwrites it with a new BSTNode, losing all the existing nodes under it. What you need is something like:

    elif i == "1":
        if current.right is None:
            current.right = BSTNode(i)
        current = current.right
    elif i == "0":
        if root.left is None:
            current.left = BSTNode(i)
        current = current.left

This will only allocate a node if there is not one already present, and then set current to this new node.