python二叉树遍历

二叉树的三种遍历方式包括前序遍历、中序遍历和后序遍历。下面是Python实现这三种遍历方式的示例代码：

# 定义二叉树节点类
class TreeNode:
    def __init__(self, value):
        self.val = value
        self.left = None
        self.right = None

# 前序遍历
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

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

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

使用示例：

# 创建二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 前序遍历
print("前序遍历：", preorderTraversal(root))  # 输出: [1, 2, 4, 5, 3]

# 中序遍历
print("中序遍历：", inorderTraversal(root))  # 输出: [4, 2, 5, 1, 3]

# 后序遍历
print("后序遍历：", postorderTraversal(root))  # 输出: [4, 5, 2, 3, 1]

以上代码实现了二叉树的前序遍历、中序遍历和后序遍历。希望能对你有所帮助！