class Node:     # 定义树节点def __init__(self, value, left=None, right=None):   # 节点的值及左子树、右子树self.value = valueself.left = leftself.right = rightclass Tree:         # 定义二叉树def __init__(self, list):self.list = listself.build_tree()def build_tree(self):      # 构建二叉树，从上到下，从左往右nodelist = []       # 构建节点列表for i in range(len(list)):nodelist.append(Node(list[i]))  # 将列表元素添加至节点列表self.root = nodelist[0]     # 树的根节点for i in range(len(list) // 2): # 遍历节点，构建二叉树nodelist[i].left = nodelist[i * 2 + 1]if i * 2 + 2 < len(nodelist):nodelist[i].right = nodelist[i * 2 + 2]def recursive_pre_order(self, nodelist, node):         # 递归前序遍历，输出顺序：父节点，左子树，右子树if node is not None:nodelist.append(node.value)self.recursive_pre_order(nodelist, node.left)self.recursive_pre_order(nodelist, node.right)return nodelistdef recursive_in_order(self, nodelist, node):         # 递归中序遍历，输出顺序：左子树，父节点，右子树if node is not None:self.recursive_in_order(nodelist, node.left)nodelist.append(node.value)self.recursive_in_order(nodelist, node.right)return nodelistdef recursive_post_order(self, nodelist, node):        # 递归后序遍历，输出顺序：左子树，右子树，父节点if node is not None:self.recursive_post_order(nodelist, node.left)self.recursive_post_order(nodelist, node.right)nodelist.append(node.value)return nodelist@staticmethoddef not_recursive_pre_order(self, node):         # 非递归前序遍历，输出顺序：父节点，左子树，右子树if node is not None:stack = [node]  # 将根节点压入栈while len(stack) > 0:print(node.value, end=" ")if node.right is not None:  # 根据栈先进后出的特点，将子节点压栈的时候，先将右子树压入栈stack.append(node.right)if node.left is not None:   # 将左子树压入栈stack.append(node.left)node = stack.pop()  # 将栈顶元素弹出@staticmethoddef not_recursive_in_order(self, node):         # 非递归中序遍历，输出顺序：左子树，父节点，右子树if node is not None:stack = []temp = node     # 将根节点复制给中间变量while temp is not None or len(stack) > 0:if temp is not None:stack.append(temp)temp = temp.left    # 中序遍历先遍历节点的左子树else:temp = stack.pop()  # 将栈顶元素弹出print(temp.value, end=" ")  # 输出栈顶元素的值temp = temp.right       # 检查右子树@staticmethoddef not_recursive_post_order(self, node):        # 非递归后序遍历，输出顺序：左子树，右子树，父节点stack1 = [node]     # 栈 1 遍历二叉树stack2 = []     # 栈 2 存储输出顺序while len(stack1) > 0:node = stack1.pop()stack2.append(node)     # 将父节点压入栈底if node.left is not None:stack1.append(node.left)    # 左子树压入栈if node.right is not None:stack1.append(node.right)   # 右子树压入栈while len(stack2) > 0:print(stack2.pop().value, end=" ")  # 输出顺序if __name__ == '__main__':list = [1, 2, 3, 4]tree = Tree(list)print("递归前序排列")retList = tree.recursive_pre_order([], tree.root)print(retList)print("非递归前序排列")tree.not_recursive_pre_order(tree, tree.root)print("\n递归中序排列")retList = tree.recursive_in_order([], tree.root)print(retList)print("非递归中序排列")tree.not_recursive_in_order(tree, tree.root)print("\n递归后序排列")retList = tree.recursive_post_order([], tree.root)print(retList)print("非递归后序排列")tree.not_recursive_post_order(tree, tree.root)