Construct String from Binary Tree

Question

A bit of a newbie to computing science.

I have the basics for a binary tree in Python:

class TreeBinary:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

This works well on insertion to popularize the tree:

root = TreeBinary(1)
root.left = TreeBinary(2)
root.right = TreeBinary(3)
root.right.right = TreeBinary(4)

One of the challenges that I am trying to discover is how to print this tree in order to show the sub-trees if there is one in the following model:

(1 (2 () ()) (3 () (4 () ())))
(2 () ())
(3 () (4 () ()))

I was able to print, but not in this format with these spaces between the sub-trees:


def show_aux(root):
    if not root:
        return ''
    string = str(root.data)
    if root.left or root.right:
        string += '(' + show_aux(root.left) + ')'
    else:
        string += '('
        string += ')'
    if root.right:
        string += '(' + show_aux(root.right) + ')'
    else:
        string += '('
        string += ')'
    return string
def show(root):
    print('(' + show_aux(root) + ')')

My results are coming out this way:

(1(2()())(3()(4()())))
(2()())
(3()(4()()))

I would like a direction to print in the expected format with the spaces between the sub-trees.

Thanks :)

Zalak Bhalani · Accepted Answer · 2021-04-29 06:53:12Z

1

Add spaces before every ( like this

def show_aux(root):
    if not root:
        return ''
    string = str(root.data)
    if root.left or root.right:
        string += ' (' + show_aux(root.left) + ')' #Space before '('
    else:
        string += ' (' #Space before '('
        string += ')'
    if root.right:
        string += ' (' + show_aux(root.right) + ')' #Space before '('
    else:
        string += ' (' #Space before '('
        string += ')'
    return string
def show(root):
    print('(' + show_aux(root) + ')')

answered Apr 29, 2021 at 6:53

Zalak Bhalani

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2 Comments

Vinicius Vasconcelos Over a year ago

Thanks. Seeing now I realize that the solution was right before my eyes.

Zalak Bhalani Over a year ago

Yes . You just needs to improve logic.

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