二叉树的递归后继函数(Python)

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

def find_successor(root, node):
    if not root:
        return None
    
    # 如果节点有右子树，后继节点是右子树的最左节点
    if node.right:
        return find_leftmost(node.right)
    
    # 如果没有右子树，向上查找直到找到一个节点是其父节点的左子节点
    successor = None
    current = root
    while current != node:
        if node.value < current.value:
            successor = current
            current = current.left
        else:
            current = current.right
    
    return successor

def find_leftmost(node):
    while node.left:
        node = node.left
    return node

# 示例用法
if __name__ == "__main__":
    root = TreeNode(2)
    root.left = TreeNode(1)
    root.right = TreeNode(3)
    
    node = root.left  # 查找节点1的后继节点
    successor = find_successor(root, node)
    if successor:
        print(f"The successor of {node.value} is {successor.value}")
    else:
        print(f"No successor found for {node.value}")