删除系统中的重复文件夹

/* 
 * 思路：
 * 1. 使用Stream API构建文件系统树。
 * 2. 使用Stream API遍历和序列化文件夹树。
 * 3. 使用Collectors和Map计算重复的文件夹。
 * 4. 使用Stream API收集剩余的文件夹路径。
 */

import java.util.*;
import java.util.stream.*;

class Solution {
    class TrieNode {
        Map<String, TrieNode> children = new HashMap<>();
        String path;
        boolean toDelete = false;

        TrieNode(String path) {
            this.path = path;
        }
    }

    public List<List<String>> deleteDuplicateFolder(List<List<String>> paths) {
        TrieNode root = new TrieNode("");
        // 构建文件系统树
        paths.forEach(path -> {
            TrieNode curr = root;
            path.forEach(folder -> curr.children.putIfAbsent(folder, new TrieNode(folder)));
        });
        Map<String, Integer> count = new HashMap<>();
        // 序列化和计数
        serialize(root, count);
        List<List<String>> result = new ArrayList<>();
        // 获取剩余文件夹
        collectRemainingFolders(root, new ArrayList<>(), result);
        return result;
    }

    private String serialize(TrieNode node, Map<String, Integer> count) {
        if (node.children.isEmpty()) {
            return "";
        }
        String serialized = node.children.values().stream()
                .map(child -> child.path + "(" + serialize(child, count) + ")")
                .sorted()
                .collect(Collectors.joining());
        count.merge(serialized, 1, Integer::sum);
        if (count.get(serialized) > 1) {
            node.toDelete = true;
        }
        return serialized;
    }

    private void collectRemainingFolders(TrieNode node, List<String> path, List<List<String>> result) {
        if (node.toDelete) {
            return;
        }
        if (!path.isEmpty()) {
            result.add(new ArrayList<>(path));
        }
        node.children.values().forEach(child -> {
            path.add(child.path);
            collectRemainingFolders(child, path, result);
            path.remove(path.size() - 1);
        });
    }
}