python遍历二叉树

class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

# 返回构造的TreeNode根节点
    def reConstructBinaryTree(self, pre, tin):
        if not pre or not tin:
            return None
        root = TreeNode(pre[0])#根节点
        # 判断输入的两个序列是不是匹配
        if set(pre) != set(tin):
            return None
        i = tin.index(root.val)    # i == 3
        root.left = self.reConstructBinaryTree(pre[1:i+1],tin[:i])  # 列表：左闭右开
        root.right = self.reConstructBinaryTree(pre[i+1:],tin[i+1:])
        return root

def BFS(self, root):   # 宽度优先遍历BFS
    array = []
    result = []
    if root == None:
        return result
    array.append(root)
    while array:
        newNode = array.pop(0)  # 根结点
        result.append(newNode.val)
        if newNode.left != None:
            array.append(newNode.left)
        if newNode.right != None:
            array.append(newNode.right)
    return result

def pre_traversal(self):
        ret = []

        def traversal(head):
            if not head:
                return
            ret.append(head.val)
            traversal(head.left)
            traversal(head.right)

        traversal(self.root)
        return ret

# 先序打印二叉树（非递归）
def preOrderTravese(node):
    stack = [node]
    while len(stack) > 0:
        print(node.val)
        if node.right is not None:
            stack.append(node.right)
        if node.left is not None:
            stack.append(node.left)
        node = stack.pop()

def in_traversal(self):
        ret = []

        def traversal(head):
            if not head:
                return
            traversal(head.left)
            ret.append(head.val)
            traversal(head.right)

        traversal(self.root)
        return ret

# 中序打印二叉树（非递归）
def inOrderTraverse(node):
    stack = []
    pos = node
    while pos is not None or len(stack) > 0:
        if pos is not None:
            stack.append(pos)
            pos = pos.left
        else:
            pos = stack.pop()
            print(pos.val)
            pos = pos.right

def post_traversal(self):
        ret = []

        def traversal(head):
            if not head:
                return
            traversal(head.left)
            traversal(head.right)
            ret.append(head.val)

        traversal(self.root)
        return ret

# 后序打印二叉树（非递归）
# 使用两个栈结构
# 第一个栈进栈顺序：左节点->右节点->跟节点
# 第一个栈弹出顺序： 跟节点->右节点->左节点(先序遍历栈弹出顺序：跟->左->右)
# 第二个栈存储为第一个栈的每个弹出依次进栈
# 最后第二个栈依次出栈
def postOrderTraverse(node):
    stack = [node]
    stack2 = []
    while len(stack) > 0:
        node = stack.pop()
        stack2.append(node)
        if node.left is not None:
            stack.append(node.left)
        if node.right is not None:
            stack.append(node.right)
    while len(stack2) > 0:
        print(stack2.pop().val)

# 二叉树的最大深度
def bTreeDepth(node):
    if node is None:
        return 0
    ldepth = bTreeDepth(node.left)
    rdepth = bTreeDepth(node.right)
    return (max(ldepth, rdepth) + 1)

# 求二叉树节点个数
def treeNodenums(node):
    if node is None:
        return 0
    nums = treeNodenums(node.left)
    nums += treeNodenums(node.right)
    return nums + 1