技術標籤：Pythonpython二叉樹

class ListNode(object):
    def __init__(self, x):
        self.val = x
        self.next = None


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

    def set_children(self, left=None, right=None)
 
:
        self.left = left
        self.right = right


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

    def pre_order(self):
        if self.root is None:
            return []
        order = []
        stack = [self.root]
        while len(stack) != 0:
 

            temp_node = stack.pop()
            order.append(temp_node.val)
            if temp_node.right is not None:
                stack.append(temp_node.right)
            if temp_node.left is not None:
                stack.append(temp_node.left)
        return order

    def middle_order(self)
 
:
        order = []
        stack = []
        temp_node = self.root
        while temp_node is not None or len(stack) != 0:
            if temp_node is not None:
                stack.append(temp_node)
                temp_node = temp_node.left
            else:
                temp_node = stack.pop()
                order.append(temp_node.val)
                temp_node = temp_node.right
        return order

    def after_order(self):
        if self.root is None:
            return []
        order = []
        stack = []
        stack.append(self.root)
        while len(stack) != 0:
            temp_node = stack.pop()
            order.append(temp_node.val)
            if temp_node.left is not None:
                stack.append(temp_node.left)
            if temp_node.right is not None:
                stack.append(temp_node.right)
        order.reverse()
        return order

    def sequence_order(self):
        if self.root is None:
            return []
        order = []
        stack = []
        stack.append(self.root)
        while len(stack) != 0:
            temp_node = stack.pop(0)
            order.append(temp_node.val)
            if temp_node.left is not None:
                stack.append(temp_node.left)
            if temp_node.right is not None:
                stack.append(temp_node.right)
        return order


node_1 = TreeNode(1)
node_2 = TreeNode(2)
node_3 = TreeNode(3)
node_1.set_children(node_2, node_3)
node_4 = TreeNode(4)
node_2.set_children(node_4)
node_5 = TreeNode(5)
node_6 = TreeNode(6)
node_3.set_children(node_5, node_6)
node_7 = TreeNode(7)
node_8 = TreeNode(8)
node_5.set_children(node_7, node_8)
tree = Tree(node_1)

# 先序遍歷：[1, 2, 4, 3, 5, 7, 8, 6]
print("先序遍歷：" + tree.pre_order().__str__())

# 中序遍歷：[4, 2, 1, 7, 5, 8, 3, 6]
print("中序遍歷：" + tree.middle_order().__str__())

# 中序遍歷：[4, 2, 7, 8, 5, 6, 3, 1]
print("後序遍歷：" + tree.after_order().__str__())

# 層序遍歷：[1, 2, 3, 4, 5, 6, 7, 8]
print("層序遍歷：" + tree.sequence_order().__str__())