二叉树前序中序后序遍历？

以下是Python实现二叉树前序、中序和后序遍历的示例代码：

1. 前序遍历（Preorder Traversal）：根节点 -> 左子树 -> 右子树

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 = []
    result.append(root.val)
    result += preorderTraversal(root.left)
    result += preorderTraversal(root.right)
    return result

# 示例用法
# 构建二叉树
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
preorder = preorderTraversal(root)
print("前序遍历结果：", preorder)

2. 中序遍历（Inorder Traversal）：左子树 -> 根节点 -> 右子树

def inorderTraversal(root):
    if root is None:
        return []
    result = []
    result += inorderTraversal(root.left)
    result.append(root.val)
    result += inorderTraversal(root.right)
    return result

# 示例用法
# 构建二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 中序遍历
inorder = inorderTraversal(root)
print("中序遍历结果：", inorder)

3. 后序遍历（Postorder Traversal）：左子树 -> 右子树 -> 根节点

def postorderTraversal(root):
    if root is None:
        return []
    result = []
    result += postorderTraversal(root.left)
    result += postorderTraversal(root.right)
    result.append(root.val)
    return result

# 示例用法
# 构建二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 后序遍历
postorder = postorderTraversal(root)
print("后序遍历结果：", postorder)