代码如下:

class TreeNode(object):
def __init__(self, data=None, left=None, right=None):
self.data = data
self.left = left
self.right = right

class Tree(object):
def __init__(self, root=None):
self.root = None

def makeTree(self, data, left, right):
self.root = TreeNode(data, left, right)

def is_empty(self):
"""是否为空 """
if self.root is None:
return True
return False

def preOrder(self, r):
"""前序遍历 """
if not r.is_empty():
print r.root.data
if r.root.left is not None:
r.preOrder(r.root.left)
if r.root.right is not None:
r.preOrder(r.root.right)

def inOrder(self, r):
"""中序遍历 """
if not r.is_empty():
if r.root.left is not None:
r.preOrder(r.root.left)
print r.root.data
if r.root.right is not None:
r.preOrder(r.root.right)

def postOrder(self, r):
"""后续遍历 """
if not r.is_empty():
if r.root.left is not None:
r.preOrder(r.root.left)
print r.root.data
if r.root.right is not None:
r.preOrder(r.root.right)

def levelOrder(self, r):
"""层级遍历 """
if not r.is_empty():
s = [r]
while len(s) > 0:
temp = s.pop(0) # 先弹出最先append到的点
if temp and temp.root is not None:
print temp.root.data
if temp.root.left is not None:
s.append(temp.root.left)
if self.root.right is not None:
s.append(temp.root.right)

def preOrder1(self, r):
"""非递归 前序遍历 """
stack = []
current = r
while len(stack) > 0 or (current and not current.is_empty()):
while current and not current.is_empty():
print current.root.data
stack.append(current)
current = current.root.left
if len(stack) > 0:
current = stack.pop()
current = current.root.right

def inOrder1(self, r):
"""非递归 中序遍历 """
stack = []
current = r
while len(stack) > 0 or (current and not current.is_empty()):
while current and not current.is_empty():
stack.append(current)
current = current.root.left
if len(stack) > 0:
current = stack.pop()
print current.root.data
current = current.root.right

def postOrder1(self, r):
"""非递归 后续遍历 """
stack = []
current = r
pre = None
while len(stack) > 0 or (current and not current.is_empty()):
if current and not current.is_empty():
stack.append(current)
current = current.root.left
elif stack[-1].root.right != pre:
current = stack[-1].root.right
pre = None
else:
pre = stack.pop()
print pre.root.data

def leaves_count(self, r):
"""求叶子节点个数 """
if r.is_empty():
return 0
elif (not r.root.left) and (not r.root.right):
return 1
else:
return r.root.left.leaves_count(r.root.left) + r.root.right.leaves_count(r.root.right)

if __name__ == '__main__':
"""二叉树"""
ra, rb, rc, rd, re, rf = Tree(), Tree(), Tree(), Tree(), Tree(), Tree()
ra.makeTree("a", None, None)
rb.makeTree("b", None, None)
rc.makeTree("c", None, None)
rd.makeTree("d", None, None)
re.makeTree("e", None, None)
rf.makeTree("f", None, None)
r1, r2, r3, r4, r = Tree(), Tree(), Tree(), Tree(), Tree()
r1.makeTree("-", rc, rd)
r2.makeTree("*", rb, r1)
r3.makeTree("+", ra, r2)
r4.makeTree("/", re, rf)
r.makeTree("-", r3, r4)
r.preOrder(r)
r.inOrder(r)
r.postOrder(r)
r.levelOrder(r)
print r.leaves_count(r)

大学的时候学过kmp算法，最近在看的时候发现竟然忘了，所以去重新看了看书，然后用python写下了这个算法：
代码如下: