b3642 二叉树的遍历python

二叉树的遍历有三种常用方法：前序遍历、中序遍历和后序遍历。下面是使用Python实现这三种遍历方法的示例代码：

# 定义二叉树节点类
class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

# 前序遍历
def preorderTraversal(root):
    if not root:
        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 not root:
        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

# 后序遍历
def postorderTraversal(root):
    if not root:
        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]

你可以根据需要调用这些函数来遍历二叉树。比如，假设有以下二叉树：

     1
   /   \
  2     3
 / \   / \
4   5 6   7

可以使用以下代码进行遍历：

# 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)
root.right.left = TreeNode(6)
root.right.right = TreeNode(7)

# 前序遍历
print("前序遍历:", preorderTraversal(root))  # 输出: [1, 2, 4, 5, 3, 6, 7]

# 中序遍历
print("中序遍历:", inorderTraversal(root))  # 输出: [4, 2, 5, 1, 6, 3, 7]

# 后序遍历
print("后序遍历:", postorderTraversal(root))  # 输出: [4, 5, 2, 6, 7, 3, 1]

希望这个示例能帮助到你！