Python BST code returning None instead of array?

Asked Dec 10 '16 at 18:05

Active Dec 10 '16 at 18:14

Viewed 19 times

I'm running a BST in Python, with the following code:

def findOdd(head):
    ary = []
    ary = BST_size(head, ary)
    print ary
    return ary

def BST_size(root, ary2):
    if root is None:
        print ary2
        return ary2
    if root.data % 2 != 0:
        print "yes"
        ary2.append(root.data)
        BST_size(root.left, ary2)
        BST_size(root.right, ary2)
    else:
        BST_size(root.left, ary2)
        BST_size(root.right, ary2)

As you can see, the goal is to return an array of the odd values within the array, however, when I run it, ary2 equals an array of the odd values, but ary simply equals None. EDIT: I changed to code to this and I'm still getting an error:

def findOdd(head):
    ary = []
    print BST_size(head, ary)
    return BST_size(head, ary)


def BST_size(root, ary2):
    if root is None:
        return ary2
    if root.data % 2 != 0 and root.data not in ary2:
        ary2.append(root.data)
        BST_size(root.left, ary2)
        BST_size(root.right, ary2)
    else:
        BST_size(root.left, ary2)
        BST_size(root.right, ary2)

edited Dec 10 '16 at 18:14

asked Dec 10 '16 at 18:05

pulsar100

1

Because your function returns `None` for the last `if`..`else` blocks. When you do not specify `return something`, `None` is returned by default. – ettanany Dec 10 '16 at 18:06
@ettanany How to fix it still will not work – pulsar100 Dec 10 '16 at 18:25
You need to return something, for example `return BST_size(root.right, ary2)` – ettanany Dec 10 '16 at 18:28
But I can only return one I cannot do: – pulsar100 Dec 10 '16 at 18:28
return BST_size(root.left, ary2) return BST_size(root.right, ary2) – pulsar100 Dec 10 '16 at 18:29
@ettanany I only get one return – pulsar100 Dec 10 '16 at 18:35
Take a step back and think about *why* you are making two recursive calls to `BST_size`. – chepner Dec 10 '16 at 18:38
@ettanany To get both sides of the tree – pulsar100 Dec 10 '16 at 18:43
You can do `return val1, val2`, but in this case I am not sure whether it is possible or not! – ettanany Dec 10 '16 at 18:57

Python BST code returning None instead of array?

0 Answers0