def post_order(node):
st1 = Stack()
st2 = Stack()
if node != None: st1.push(node)
while not st1.is_empty():
n = st1.pop()
st2.push(n)
if n.left != None: st1.push(n.left)
if n.right != None: st1.push(n.right)
while not st2.is_empty():
n = st2.pop()
print(n.data, end=' ')
print()
return
def pre_order(node):
stk = Stack()
if node != None: stk.push(node)
while not stk.is_empty():
n = stk.pop()
print(n.data, end=' ')
if n.right != None: stk.push(n.right)
if n.left != None: stk.push(n.left)
print()
return