打印子节点

class TreeNode:
    def __init__(self, value):
        self.value = value
        self.children = []

    def add_child(self, child_node):
        self.children.append(child_node)

# 创建一个示例树
root = TreeNode('Root')
child1 = TreeNode('Child1')
child2 = TreeNode('Child2')
subchild1 = TreeNode('Subchild1')

root.add_child(child1)
root.add_child(child2)
child1.add_child(subchild1)

def print_children(node):
    for child in node.children:
        print(child.value)

# 调用函数打印根节点的子节点
print_children(root)

def safe_print_children(node):
    if node.children:
        for child in node.children:
            print(child.value)
    else:
        print("No children found.")

def print_children_avoid_cycle(node, visited=None):
    if visited is None:
        visited = set()
    if node in visited:
        return
    visited.add(node)
    for child in node.children:
        print(child.value)
        print_children_avoid_cycle(child, visited)  # 递归调用时要传递visited集合