如何将数据结构转换为另一种树结构

def build_tree(data, parent_id=None):
    tree = []
    for item in data:
        if item['parent_id'] == parent_id:
            children = build_tree(data, item['id'])
            if children:
                item['children'] = children
            tree.append(item)
    return tree

# 示例数据
data = [
    {'id': 1, 'name': 'A', 'parent_id': None},
    {'id': 2, 'name': 'B', 'parent_id': 1},
    {'id': 3, 'name': 'C', 'parent_id': 1},
    {'id': 4, 'name': 'D', 'parent_id': 2},
]

tree = build_tree(data)
print(tree)

def build_tree_with_cycle_detection(data, parent_id=None, visited=None):
    if visited is None:
        visited = set()
    tree = []
    for item in data:
        if item['id'] in visited:
            continue
        if item['parent_id'] == parent_id:
            visited.add(item['id'])
            children = build_tree_with_cycle_detection(data, item['id'], visited)
            if children:
                item['children'] = children
            tree.append(item)
    return tree

# 示例数据（包含循环引用）
data_with_cycle = [
    {'id': 1, 'name': 'A', 'parent_id': None},
    {'id': 2, 'name': 'B', 'parent_id': 1},
    {'id': 3, 'name': 'C', 'parent_id': 1},
    {'id': 4, 'name': 'D', 'parent_id': 2},
    {'id': 2, 'name': 'B2', 'parent_id': 4},  # 循环引用
]

tree_with_cycle = build_tree_with_cycle_detection(data_with_cycle)
print(tree_with_cycle)