Write code IN PYTHON to implement a function that will compute the number of nod

Question

Write code IN PYTHON to implement a function that will compute the number of nodes in a binary tree. Call the function treeNodes(root). Test your code with at least three trees that you can create using expressions and the buildParseTree function.

here is the buildParseTree function:

from pythonds.basic.stack import Stack
from pythonds.trees.binaryTree import BinaryTree

def buildParseTree(fpexp):
fplist = fpexp.split()
pStack = Stack()
eTree = BinaryTree('')
pStack.push(eTree)
currentTree = eTree
for i in fplist:
if i == '(':
currentTree.insertLeft('')
pStack.push(currentTree)
currentTree = currentTree.getLeftChild()
elif i not in ['+', '-', '*', '/', ')']:
currentTree.setRootVal(int(i))
parent = pStack.pop()
currentTree = parent
elif i in ['+', '-', '*', '/']:
currentTree.setRootVal(i)
currentTree.insertRight('')
pStack.push(currentTree)
currentTree = currentTree.getRightChild()
elif i == ')':
currentTree = pStack.pop()
else:
raise ValueError
return eTree

pt = buildParseTree("( ( 10 + 5 ) * 3 )")
pt.postorder() #defined and explained in the next section

Explanation / Answer

def BST_size(root):
if root is None:
return -1
if root is not None:
if root.left is not None:
return 1 + BST_size(root.left)
if root.right is not None:
return 1 + BST_size(root.right)
def print_BST_size(root):
size = BST_size(root)
if size == -1:
print "size -1 (Null value in root)"
else:
print "size", size

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