Skip to content

1166. Design File System πŸ”’

Description

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

The format of a path is one 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 empty string "" and "/" are not.

Implement the FileSystem class:

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

 

Example 1:

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:

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 <= 109
  • Each path is valid and consists of lowercase English letters and '/'.
  • At most 104 calls in total will be made to createPath and get.

Solutions

Solution 1: Trie

We can use a trie to store the paths, where each node stores a value, representing the value of the path corresponding to the node.

The structure of the trie node is defined as follows:

  • children: Child nodes, stored in a hash table, where the key is the path of the child node, and the value is the reference to the child node.
  • v: The value of the path corresponding to the current node.

The methods of the trie are defined as follows:

  • insert(w, v): Insert the path $w$ and set its corresponding value to $v$. If the path $w$ already exists or its parent path does not exist, return false, otherwise return true. The time complexity is $O(|w|)$, where $|w|$ is the length of the path $w$.
  • search(w): Return the value corresponding to the path $w$. If the path $w$ does not exist, return $-1$. The time complexity is $O(|w|)$.

The total time complexity is $O(\sum_{w \in W}|w|)$, and the total space complexity is $O(\sum_{w \in W}|w|)$, where $W$ is the set of all inserted paths.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
class Trie:
    def __init__(self, v: int = -1):
        self.children = {}
        self.v = v

    def insert(self, w: str, v: int) -> bool:
        node = self
        ps = w.split("/")
        for p in ps[1:-1]:
            if p not in node.children:
                return False
            node = node.children[p]
        if ps[-1] in node.children:
            return False
        node.children[ps[-1]] = Trie(v)
        return True

    def search(self, w: str) -> int:
        node = self
        for p in w.split("/")[1:]:
            if p not in node.children:
                return -1
            node = node.children[p]
        return node.v


class FileSystem:
    def __init__(self):
        self.trie = Trie()

    def createPath(self, path: str, value: int) -> bool:
        return self.trie.insert(path, value)

    def get(self, path: str) -> int:
        return self.trie.search(path)


# Your FileSystem object will be instantiated and called as such:
# obj = FileSystem()
# param_1 = obj.createPath(path,value)
# param_2 = obj.get(path)
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
class Trie {
    Map<String, Trie> children = new HashMap<>();
    int v;

    Trie(int v) {
        this.v = v;
    }

    boolean insert(String w, int v) {
        Trie node = this;
        var ps = w.split("/");
        for (int i = 1; i < ps.length - 1; ++i) {
            var p = ps[i];
            if (!node.children.containsKey(p)) {
                return false;
            }
            node = node.children.get(p);
        }
        if (node.children.containsKey(ps[ps.length - 1])) {
            return false;
        }
        node.children.put(ps[ps.length - 1], new Trie(v));
        return true;
    }

    int search(String w) {
        Trie node = this;
        var ps = w.split("/");
        for (int i = 1; i < ps.length; ++i) {
            var p = ps[i];
            if (!node.children.containsKey(p)) {
                return -1;
            }
            node = node.children.get(p);
        }
        return node.v;
    }
}

class FileSystem {
    private Trie trie = new Trie(-1);

    public FileSystem() {
    }

    public boolean createPath(String path, int value) {
        return trie.insert(path, value);
    }

    public int get(String path) {
        return trie.search(path);
    }
}

/**
 * Your FileSystem object will be instantiated and called as such:
 * FileSystem obj = new FileSystem();
 * boolean param_1 = obj.createPath(path,value);
 * int param_2 = obj.get(path);
 */
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
class Trie {
public:
    unordered_map<string, Trie*> children;
    int v;

    Trie(int v) {
        this->v = v;
    }

    bool insert(string& w, int v) {
        Trie* node = this;
        auto ps = split(w, '/');
        for (int i = 1; i < ps.size() - 1; ++i) {
            auto p = ps[i];
            if (!node->children.count(p)) {
                return false;
            }
            node = node->children[p];
        }
        if (node->children.count(ps.back())) {
            return false;
        }
        node->children[ps.back()] = new Trie(v);
        return true;
    }

    int search(string& w) {
        Trie* node = this;
        auto ps = split(w, '/');
        for (int i = 1; i < ps.size(); ++i) {
            auto p = ps[i];
            if (!node->children.count(p)) {
                return -1;
            }
            node = node->children[p];
        }
        return node->v;
    }

private:
    vector<string> split(string& s, char delim) {
        stringstream ss(s);
        string item;
        vector<string> res;
        while (getline(ss, item, delim)) {
            res.emplace_back(item);
        }
        return res;
    }
};

class FileSystem {
public:
    FileSystem() {
        trie = new Trie(-1);
    }

    bool createPath(string path, int value) {
        return trie->insert(path, value);
    }

    int get(string path) {
        return trie->search(path);
    }

private:
    Trie* trie;
};

/**
 * 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);
 */
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
type trie struct {
    children map[string]*trie
    v        int
}

func newTrie(v int) *trie {
    return &trie{map[string]*trie{}, v}
}

func (t *trie) insert(w string, v int) bool {
    node := t
    ps := strings.Split(w, "/")
    for _, p := range ps[1 : len(ps)-1] {
        if _, ok := node.children[p]; !ok {
            return false
        }
        node = node.children[p]
    }
    if _, ok := node.children[ps[len(ps)-1]]; ok {
        return false
    }
    node.children[ps[len(ps)-1]] = newTrie(v)
    return true
}

func (t *trie) search(w string) int {
    node := t
    ps := strings.Split(w, "/")
    for _, p := range ps[1:] {
        if _, ok := node.children[p]; !ok {
            return -1
        }
        node = node.children[p]
    }
    return node.v
}

type FileSystem struct {
    trie *trie
}

func Constructor() FileSystem {
    return FileSystem{trie: newTrie(-1)}
}

func (this *FileSystem) CreatePath(path string, value int) bool {
    return this.trie.insert(path, value)
}

func (this *FileSystem) Get(path string) int {
    return this.trie.search(path)
}

/**
 * Your FileSystem object will be instantiated and called as such:
 * obj := Constructor();
 * param_1 := obj.CreatePath(path,value);
 * param_2 := obj.Get(path);
 */
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
class Trie {
    children: Map<string, Trie>;
    v: number;

    constructor(v: number) {
        this.children = new Map<string, Trie>();
        this.v = v;
    }

    insert(w: string, v: number): boolean {
        let node: Trie = this;
        const ps = w.split('/').slice(1);
        for (let i = 0; i < ps.length - 1; ++i) {
            const p = ps[i];
            if (!node.children.has(p)) {
                return false;
            }
            node = node.children.get(p)!;
        }
        if (node.children.has(ps[ps.length - 1])) {
            return false;
        }
        node.children.set(ps[ps.length - 1], new Trie(v));
        return true;
    }

    search(w: string): number {
        let node: Trie = this;
        const ps = w.split('/').slice(1);
        for (const p of ps) {
            if (!node.children.has(p)) {
                return -1;
            }
            node = node.children.get(p)!;
        }
        return node.v;
    }
}

class FileSystem {
    trie: Trie;

    constructor() {
        this.trie = new Trie(-1);
    }

    createPath(path: string, value: number): boolean {
        return this.trie.insert(path, value);
    }

    get(path: string): number {
        return this.trie.search(path);
    }
}

/**
 * Your FileSystem object will be instantiated and called as such:
 * var obj = new FileSystem()
 * var param_1 = obj.createPath(path,value)
 * var param_2 = obj.get(path)
 */

Comments