71. Simplify Path

Problem Statement

link: https://leetcode.com/problems/simplify-path/ https://leetcode.cn/problems/simplify-path/

Given a string path, which is an absolute path (starting with a slash ‘/’) to a file or directory in a Unix-style file system, convert it to the simplified canonical path.

In a Unix-style file system, a period ‘.’ refers to the current directory, a double period ‘..’ refers to the directory up a level, and any multiple consecutive slashes (i.e. ‘//’) are treated as a single slash ‘/’. For this problem, any other format of periods such as ‘…’ are treated as file/directory names.

The canonical path should have the following format:

The path starts with a single slash ‘/’. Any two directories are separated by a single slash ‘/’. The path does not end with a trailing ‘/’. The path only contains the directories on the path from the root directory to the target file or directory (i.e., no period ‘.’ or double period ‘..’) Return the simplified canonical path.

Example:

Input: path = "/home/" Output: /home

Input: path = "/../" Output: /

Solution Approach

The solution employs a stack to simplify Unix-style paths.

Algorithm

1. Initialization: Use an empty list, res, as a stack to hold directory names.
2. Path Tokenization: Split the path by slashes, while eliminating trailing slashes.
3. Token Handling: Skip ‘.’ or empty tokens; pop for ‘..’; push any other tokens onto the stack.

Implement

    class Solution:
        def simplifyPath(self, path: str) -> str:
          res = []
          for it in path.rstrip("/").split("/"):
              if it == "." or it == "":
                  continue
              elif it == "..":
                  if len(res) > 0:
                      res.pop()
              else:
                  res.append(it)
          return '/' + '/'.join(res)
 

    
    

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