1166. Design File System

Design File System - LeetCode

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.


The number of calls to the two functions is less than or equal to 104 in total.
2 <= path.length <= 100
1 <= value <= 109

  • code
class TrieNode:
    def __init__(self):
        self.map = defaultdict(TrieNode)
        self.value = -1
class FileSystem:

    def __init__(self):
        self.root = TrieNode()

    def createPath(self, path: str, value: int) -> bool:
        cur_node = self.root
        path_list = path[1:].split("/")
        for idx, path in enumerate(path_list):
            if path not in cur_node.map:
                if idx != len(path_list) - 1: return False
                cur_node.map[path] = TrieNode()
            cur_node = cur_node.map[path]
        if cur_node.value != -1: return False
        cur_node.value = value
        return True

    def get(self, path: str) -> int:
        cur_node = self.root
        path_list = path.split("/")
        for i in range(1, len(path_list)):
            if path_list[i] not in cur_node.map: return -1
            cur_node = cur_node.map[path_list[i]]
        return cur_node.value