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1233. Remove Sub-Folders from the Filesystem

Posted on Edited on In Disqus:
Symbols count in article: 1.9k Reading time ≈ 2 mins.

用hash table提前把所有path存起来 遍历每个path 从后往前删文件名（相当于从subfolder向上找parent folder的path）如果parent folder的path在hash table里 证明这是一个subfolder应该remove 否则将一直找到根目录的path

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class Solution {
public:
    vector<string> removeSubfolders(vector<string>& folder) {
        unordered_set<string_view> s(begin(folder), end(folder));
        vector<string> res;
        for (const auto &f : folder) {
            string_view v(f);
            do {
                v.remove_suffix(v.length() - v.find_last_of('/'));
            } while (!v.empty() && !s.count(v));
            if (v.empty()) {
                res.push_back(f);
            }
        }
        return res;
    }
};
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class Solution {
public:
    vector<string> removeSubfolders(vector<string>& folder) {
        unordered_set<string_view> s(begin(folder), end(folder));
        vector<string> res;
        for (const auto &f : folder) {
            string_view v(f);
            while (!v.empty()) {
                while (v.back() != '/') {
                    v.remove_suffix(1);
                }
                v.remove_suffix(1);
                if (s.count(v)) break;
            }
            if (v.empty()) {
                res.push_back(f);
            }
        }
        return res;
    }
};

类似trie

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class Solution {
public:
    vector<string> removeSubfolders(vector<string>& folder) {
        root = new Folder;
        for (const auto &path : folder) {
            add(path);
        }
        dfs(root);
        return res;
    }

    struct Folder {
        unordered_map<string, Folder *> subfolders;
        string path;
    };

    Folder *root;

    void add(const string &path) {
        auto p = root;
        istringstream input(path);
        string name;
        while (getline(input, name, '/')) {
            if (!p->subfolders.count(name)) {
                p->subfolders[name] = new Folder;
            }
            p = p->subfolders[name];
        }
        p->path = path;
    }

    void dfs(Folder *p) {
        if (!p->path.empty()) {
            res.push_back(p->path);
            return;
        }
        for (auto &[_, subfolder] : p->subfolders) {
            dfs(subfolder);
        }
    }

    vector<string> res;
};