1166. Design File System

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1166. Design File System

Description

You are asked to design a file systemthat allows you to create new paths and associate them with different values.

The format of a path isone or more concatenated strings of the form:/ followed by one or more lowercase English letters. For example, “/leetcode"and “/leetcode/problems"are valid paths while an emptystring "" and "/"are not.

Implement theFileSystem class:

  • bool createPath(string path, int value)Creates a new path and associates a value to it if possible and returns true.Returns falseif the path already exists or its parent path doesn’t exist .
  • int get(string path)Returns the value associated with path or returns-1if the path doesn’t exist.

Example 1:

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Input:
["FileSystem","createPath","get"]
[[],["/a",1],["/a"]]
Output:
[null,true,1]
Explanation:
FileSystem fileSystem = new FileSystem();

fileSystem.createPath("/a", 1); // return true
fileSystem.get("/a"); // return 1

Example 2:

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Input:
["FileSystem","createPath","createPath","get","createPath","get"]
[[],["/leet",1],["/leet/code",2],["/leet/code"],["/c/d",1],["/c"]]
Output:
[null,true,true,2,false,-1]
Explanation:
FileSystem fileSystem = new FileSystem();

fileSystem.createPath("/leet", 1); // return true
fileSystem.createPath("/leet/code", 2); // return true
fileSystem.get("/leet/code"); // return 2
fileSystem.createPath("/c/d", 1); // return false because the parent path "/c" doesn't exist.
fileSystem.get("/c"); // return -1 because this path doesn't exist.

Constraints:

  • 2 <= path.length <= 100
  • 1 <= value <= 10^9
  • Each path is valid and consists of lowercase English letters and '/'.
  • At most 10^4 calls in total will be made to createPath and get.

Hints/Notes

Solution

Language: C++

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class FileSystem {
public:
    struct TrieNode {
        TrieNode(string name = ""): name(name) {}

        string name;
        int val = -1;
        unordered_map<string, TrieNode*> m;
    };

    TrieNode* root;

    FileSystem() {
        root = new TrieNode();
    }

    bool createPath(string path, int value) {
        vector<string> components = getComponents(path);
        if (components.size() == 0) {
            return false;
        }
        TrieNode* cur = root;
        int n = components.size();
        for (int i = 0; i < n - 1; i++) {
            string& c = components[i];
            if (!cur->m.contains(c)) {
                return false;
            }
            cur = cur->m[c];
        }
        string new_path = components[n - 1];
        if (cur->m.contains(new_path)) {
            return false;
        } else {
            cur->m[new_path] = new TrieNode(new_path);
            cur->m[new_path]->val = value;
            return true;
        }
    }

    int get(string path) {
        vector<string> components = getComponents(path);
        int n = components.size();
        TrieNode* cur = root;
        for (int i = 0; i < n; i++) {
            string& c = components[i];
            if (!cur->m.contains(c)) {
                return -1;
            }
            cur = cur->m[c];
        }
        return cur->val;
    }

    vector<string> getComponents(string path) {
        int start = 1, end;
        vector<string> components;
        while ((end = path.find('/', start)) != string::npos) {
            components.push_back(path.substr(start, end - start));
            start = end + 1;
        }
        components.push_back(path.substr(start));
        return components;
    }
};

/**
 * Your FileSystem object will be instantiated and called as such:
 * FileSystem* obj = new FileSystem();
 * bool param_1 = obj->createPath(path,value);
 * int param_2 = obj->get(path);
 */