stack.append(treenode)
treenode = treenode.left
else:
treenode = stack.pop()
print treenode.data
treenode = treenode.right
def postorders(self, treenode):
'后序（post-order，LRN）非递归遍历'
stack = []
pre = 0
while treenode or stack:
if treenode:
stack.append(treenode)
treenode = treenode.left
elif stack[-1].right != pre:
treenode = stack[-1].right
pre = 0
else:
pre = stack.pop()
print pre.data
# def postorders(self, treenode):
# '后序（post-order，LRN）非递归遍历'
# stack = []
# queue = []
# queue.append(treenode)
# while queue:
# treenode = queue.pop()
# if treenode.left:
# queue.append(treenode.left)
# if treenode.right:
# queue.append(treenode.right)
# stack.append(treenode)
