class BinaryTree:
def __init__(self, root_obj):
self.key = root_obj
self.left_child = None
self.right_child = None
def insert_left(self, new_node):
if self.left_child == None:
self.left_child = BinaryTree(new_node)
else:
t = BinaryTree(new_node)
t.left_child = self.left_child
self.left_child = t
def insert_right(self, new_node):
if self.right_child == None:
self.right_child = BinaryTree(new_node)
else:
t = BinaryTree(new_node)
t.right_child = self.right_child
self.right_child = t
def get_left_child(self):
return self.left_child
def get_right_child(self):
return self.right_child
def set_root_val(self, obj):
self.key = obj
def get_root_val(self):
return self.key
def preOrder(self):
print(self.key)
if self.left_child:
self.left_child.preOrder()
if self.right_child:
self.right_child.preOrder()
def postOrder(self):
if self.left_child:
self.left_child.postOrder()
if self.right_child:
self.right_child.postOrder()
print(self.key)
def inOrder(self):
if self.left_child:
self.left_child.inOrder()
print(self.key)
if self.right_child:
self.right_child.inOrder()
def build_parse_tree(fpexpr):
fp_list = fpexpr.split()
pstack = Stack()
eTree = BinaryTree('')
pstack.push(eTree)
current_node = eTree
for i in fp_list:
if i == '(':
current_node.insert_left('')
pstack.push(current_node)
current_node = current_node.get_left_child()
elif i not in ['+', '-', '*', '/', ')']:
current_node.set_root_val(int(i))
parent = pstack.pop()
current_node = parent
elif i in ['+', '-', '*', '/']:
current_node = set_root_val(i)
current_node.insert_right('')
pstack.push(current_node)
current_node = current_node.get_right_child()
elif i == ')':
current_node = pstack.pop()
else:
raise ValueError
return eTree
def evaluate(build_parse_tree):
opers = {'+':+,'-':-,'*':*,'/':/}
leftC = build_parse_tree.get_left_child()
rightC = build_parse_tree.get_right_child()
if leftC and rightC:
fn = opers[build_parse_tree.get_root_val()]
return fn(evaluate(leftC), evaluate(rightC))
else:
return build_parse_tree.get_root_val()
def postOrderEval(build_parse_tree):
opers = {'+':+, '-':-, '*':*, '/':/}
res1 = None
res2 = None
if build_parse_tree != None #or if build_parse_tree:
res1 = postOrderEval(build_parse_tree.get_left_child())
res2 = postOrderEval(build_parse_tree.get_right_child())
if res1 and res2:
return opers[build_parse_tree.get_root_val()](res1, res2)
else:
return build_parse_tree.get_root_val()
