Python 3.x

treenode.py

# Defines the tree node ADT # # A treenode is a simple container with three pieces of information # data: the contained information # left: a reference to another treenode or None # right: a reference to another treenode or None

# Implementation notes: # This implementation uses a Python dictionary as a record.

def create(data, left=None, right=None): """ Create a new treenode for the given data. Pre-conditions: data: Any data value to be stored in the treenode left: Another treenode (or None, by default) Post-condition: none Return: the treenode created """ return {'data':data, 'left':left, 'right':right}

def get_data(treenode): """ Retrieve the contents of the data field. Pre-conditions: node: a node created by create() Post-conditions: none Return the data value stored previously in the node """ return treenode['data']

def get_left(tnode): """ Retrieve the contents of the left field. Pre-conditions: tnode: a treenode created by create() Post-conditions: none Return the value stored in left field """ return tnode['left']

def get_right(tnode): """ Retrieve the contents of the right field. Pre-conditions: tnode: a treenode created by create() Post-conditions: none Return the value stored in right field """ return tnode['right']

def set_data(tnode, val): """ Set the contents of the data field to val. Pre-conditions: tnode: a node created by create() val: a data value to be stored Post-conditions: stores the new data value, replacing the existing value Return none """ tnode['data'] = val

def set_left(tnode, val): """ Set the contents of left field to val. Pre-conditions: tnode: a treenode created by create() val: a treenode, or the value None Post-conditions: stores the val in left field, replacing the existing value Return none """ tnode['left'] = val

def set_right(tnode, val): """ Set the contents of right field to val. Pre-conditions: tnode: a treenode created by create() val: a treenode, or the value None Post-conditions: stores the val in right field, replacing the existing value Return none """ tnode['right'] = val