Leetcode #71: Simplify Path
In this guide, we solve Leetcode #71 Simplify Path 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 given an absolute path for a Unix-style file system, which always begins with a slash '/'. Your task is to transform this absolute path into its simplified canonical path.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Stack, String
Intuition
The problem has a natural nested or last-in-first-out structure.
A stack lets us resolve matches in the correct order as we scan.
Approach
Push items as they appear and pop when you can finalize a decision.
The stack captures the unresolved part of the input.
Steps:
- Push elements as you scan.
- Pop when a rule or match is satisfied.
- Use the stack to compute results.
Python Solution
class Solution:
def simplifyPath(self, path: str) -> str:
stk = []
for s in path.split('/'):
if not s or s == '.':
continue
if s == '..':
if stk:
stk.pop()
else:
stk.append(s)
return '/' + '/'.join(stk)
Complexity
The time complexity is and the space complexity is , where is the length of the path. The space complexity is , where is the length of the path.
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.