leetcode - 1166. Design File System

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:

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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:

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2 <= path.length <= 100
1 <= value <= 10^9
Each path is valid and consists of lowercase English letters and '/'.
At most 104 calls in total will be made to createPath and get.

Solution

Trie tree

Code

python3 复制代码

class TrieNode:
    def __init__(self, val: int):
        self.child = {}
        self.val = val

class FileSystem:

    def __init__(self):
        self.root = TrieNode(-1)

    def createPath(self, path: str, value: int) -> bool:
        paths = path.split('/')[1:]
        node = self.root
        for each_path in paths[:-1]:
            if each_path not in node.child:
                return False
            node = node.child[each_path]
        if paths[-1] in node.child:
            return False
        # create the last directory
        node.child[paths[-1]] = TrieNode(value)
        return True
        

    def get(self, path: str) -> int:
        node = self.root
        paths = path.split('/')[1:]
        for each_path in paths:
            if each_path in node.child:
                node = node.child[each_path]
            else:
                return -1
        return node.val


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