588. Design In-Memory File System

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588. Design In-Memory File System

Description

Design a data structure that simulates an in-memory file system.

Implement the FileSystem class:

  • FileSystem() Initializes the object of the system.

  • List<String> ls(String path)

  • If path is a file path, returns a list that only contains this file’s name.

  • If path is a directory path, returns the list of file and directory names in this directory .

The answer should in lexicographic order .

  • void mkdir(String path) Makes a new directory according to the given path. The given directory path does not exist. If the middle directories in the path do not exist, you should create them as well.

  • void addContentToFile(String filePath, String content)

  • If filePath does not exist, creates that file containing given content.

  • If filePath already exists, appends the given content to original content.

  • String readContentFromFile(String filePath) Returns the content in the file at filePath.

Example 1:

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Input

["FileSystem", "ls", "mkdir", "addContentToFile", "ls", "readContentFromFile"]
[[], ["/"], ["/a/b/c"], ["/a/b/c/d", "hello"], ["/"], ["/a/b/c/d"]]
Output

[null, [], null, null, ["a"], "hello"]

Explanation

FileSystem fileSystem = new FileSystem();
fileSystem.ls("/");                         // return []
fileSystem.mkdir("/a/b/c");
fileSystem.addContentToFile("/a/b/c/d", "hello");
fileSystem.ls("/");                         // return ["a"]
fileSystem.readContentFromFile("/a/b/c/d"); // return "hello"

Constraints:

  • 1 <= path.length,filePath.length <= 100
  • path and filePathare absolute paths which begin with '/'and do not end with '/'except that the path is just"/".
  • You can assume that all directory names and file names only contain lowercase letters, and the same names will not exist in the same directory.
  • You can assume that all operations will be passed valid parameters, and users will not attempt to retrieve file content or list a directory or file that does not exist.
  • You can assume that the parent directory for the file in addContentToFile will exist.
  • 1 <= content.length <= 50
  • At most 300 calls will be made to ls, mkdir,addContentToFile, andreadContentFromFile.

Hints/Notes

Solution

Language: C++

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class FileSystem {
public:
    struct Object {
        Object(string name) {
            this->name = name;
            isFile = false;
        }
        unordered_map<string, Object*> children;
        bool isFile = false;
        string name;
        string fileContent;
    };

    Object* root;

    FileSystem() {
        root = new Object("root");
    }

    vector<string> ls(string path) {
        vector<string> names = parsePath(path);
        Object* curNode = root;
        for (auto& name : names) {
            curNode = curNode->children[name];
        }
        set<string> res;
        if (curNode->isFile) {
            res.insert(curNode->name);
        } else {
            for (auto [k, _] : curNode->children) {
                res.insert(k);
            }
        }
        return vector<string>(res.begin(), res.end());
    }

    void mkdir(string path) {
        vector<string> names = parsePath(path);
        Object* curNode = root;
        for (auto& name : names) {
            if (!curNode->children.contains(name)) {
                curNode->children[name] = new Object(name);
            }
            curNode = curNode->children[name];
        }
    }

    void addContentToFile(string filePath, string content) {
        vector<string> names = parsePath(filePath);
        Object* curNode = root;
        for (auto& name : names) {
            if (!curNode->children.contains(name)) {
                curNode->children[name] = new Object(name);
            }
            curNode = curNode->children[name];
        }
        curNode->isFile = true;
        curNode->fileContent += content;
    }

    string readContentFromFile(string filePath) {
        vector<string> names = parsePath(filePath);
        Object* curNode = root;
        for (auto& name : names) {
            if (!curNode->children.contains(name)) {
                curNode->children[name] = new Object("name");
            }
            curNode = curNode->children[name];
        }
        return curNode->fileContent;
    }

    vector<string> parsePath(string& filePath) {
        vector<string> names;
        int start = 1, end;
        while ((end = filePath.find('/', start)) != string::npos) {
            names.push_back(filePath.substr(start, end - start));
            start = end + 1;
        }
        if (start < filePath.size()) {
            names.push_back(filePath.substr(start));
        }
        return names;
    }
};

/**
 * Your FileSystem object will be instantiated and called as such:
 * FileSystem* obj = new FileSystem();
 * vector<string> param_1 = obj->ls(path);
 * obj->mkdir(path);
 * obj->addContentToFile(filePath,content);
 * string param_4 = obj->readContentFromFile(filePath);
 */