Leetcode #1166: Design File System
In this guide, we solve Leetcode #1166 Design File System in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
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.
Quick Facts
- Difficulty: Medium
- Premium: Yes
- Tags: Design, Trie, Hash Table, String
Intuition
Fast membership checks and value lookups are the heart of this problem, which makes a hash map the natural choice.
By storing what we have already seen (or counts/indexes), we can answer the question in one pass without backtracking.
Approach
Scan the input once, using the map to detect when the condition is satisfied and to update state as you go.
This keeps the solution linear while remaining easy to explain in an interview setting.
Steps:
- Initialize a hash map for seen items or counts.
- Iterate through the input, querying/updating the map.
- Return the first valid result or the final computed value.
Example
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
Python Solution
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)
Complexity
The time complexity is , where is the length of the path . The space complexity is O(n).
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.