【Python】二叉树遍历
【Python】二叉树遍历
广度遍历（层次遍历）
非递归：用队列实现
def traverse(self, tree):
if not tree:
return []
res = []
q = Queue.Queue()
q.put(tree)
while not q.empty():
level = []
length = q.qsize()
for i in range(length):
p = q.get()
level.append(p.val)
if p.left:
q.put(p.left)
if p.right:
q.put(p.right)
res.append(level)
return res深度遍历
- 前序遍历
前序遍历（根结点–>左结点–>右结点）
递归
def PreOrder(self, tree, res):
if not tree:
return []
res.append(tree.val)
self.PreOrder(tree.left, res)
self.PreOrder(tree.right, res)
return res非递归：用栈实现
def preorder(self, bintree):
if not bintree:
return []
res = []
tree = []
p = bintree
while p or tree:
while p:
tree.append(p)
res.append(p.val)
p = p.left
if tree:
p = tree.pop()
p = p.right
return res- 中序遍历
中序遍历（左结点–>根结点–>右结点）
递归
def InOrder(self, tree, res):
if not tree:
return []
self.InOrder(tree.left, res)
res.append(tree.val)
self.InOrder(tree.right, res)
return res非递归：用栈实现
def inorder(self, bintree):
if not bintree:
return []
res = []
tree = []
p = bintree
while p or tree:
while p:
tree.append(p)
p = p.left
if tree:
p = tree.pop()
res.append(p.val)
p = p.right
return res- 后序遍历
后序遍历（左结点–>右结点–>根结点）
递归
def PostOrder(self, tree, res):
if not tree:
return []
self.PostOrder(tree.left, res)
self.PostOrder(tree.right, res)
res.append(tree.val)
return res非递归：用栈实现
def postorder(self, bintree):
if not bintree:
return []
tree = []
res = []
tree.append(bintree)
while tree:
p = tree.pop()
res.insert(0, p.val)
if p.left:
tree.append(p.left)
if p.right:
tree.append(p.right)
return res