完全二叉树的输出序列便利

完全二叉树的输出序列遍历有三种方式：前序遍历、中序遍历和后序遍历。下面是对完全二叉树进行这三种遍历的示例代码：

1. 前序遍历：

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def preorderTraversal(root):
    if root is None:
        return []
    result = []
    stack = [root]
    while stack:
        node = stack.pop()
        result.append(node.val)
        if node.right:
            stack.append(node.right)
        if node.left:
            stack.append(node.left)
    return result

# 创建一个完全二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)
root.right.left = TreeNode(6)

# 前序遍历输出序列
print(preorderTraversal(root))  # 输出：[1, 2, 4, 5, 3, 6]

2. 中序遍历：

def inorderTraversal(root):
    if root is None:
        return []
    result = []
    stack = []
    node = root
    while stack or node:
        while node:
            stack.append(node)
            node = node.left
        node = stack.pop()
        result.append(node.val)
        node = node.right
    return result

# 中序遍历输出序列
print(inorderTraversal(root))  # 输出：[4, 2, 5, 1, 6, 3]

3. 后序遍历：

def postorderTraversal(root):
    if root is None:
        return []
    result = []
    stack = [root]
    while stack:
        node = stack.pop()
        result.append(node.val)
        if node.left:
            stack.append(node.left)
        if node.right:
            stack.append(node.right)
    return result[::-1]

# 后序遍历输出序列
print(postorderTraversal(root))  # 输出：[4, 5, 2, 6, 3, 1]