CODEWITHSUNDEEP
pythontreenumbersbinary-tree
lilbanili
lilbanili

Reputation: 137

Subtracting branches of a Binary Number Tree in python

So like I have this problem and I have no idea how to do it at all. The problem goes like this:

Define a recursive function called subt_tree() that takes a Binary-Number-Tree and recursively subtracts the value of each right branch from the left branch. So for example, if 

tree1 = (25,((10,4),(12,11)))

then subt_tree(tree1) would return

( 25 - ( (10-4) - (12-11) ) ) = ( 25 - ( 6 - 1 ) ) = ( 25 - 5 ) = 20.

So essentially I have to make each tuple into a subtraction problem and then solve.

I've tried this:

def subt_tree(bnt):
    """Takes a bnt and recursively subtracts the value of each right branch from the left branch.

    bnt -> number"""
    if not isinstance(bnt,tuple):
        return 1
    else:
        return subt_tree(bnt[0]) - subt_tree(bnt[1])

but there must be something wrong in my else statement because no matter what I input it will only return 0 or 1.

Upvotes: 0

Views: 286

Answers (1)

Paul Rooney
Paul Rooney

Reputation: 21619

Instead of returning 1 why don't you return the value itself? That is after all the base case for your recursion.

i.e.

def subt_tree(bnt):
    if not isinstance(bnt,tuple):
        return bnt
    else:
        return subt_tree(bnt[0]) - subt_tree(bnt[1])

If you return 1 you'll only ever get a set of values consisting of 1 being subtracted from each other.

Upvotes: 2

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