Skip to content

71. Simplify Path

String Stack

Problem - Simplify Path

Medium

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.

The rules of a Unix-style file system are as follows:

  • A single period '.' represents the current directory.
  • A double period '..' represents the previous/parent directory.
  • Multiple consecutive slashes such as '//' and '///' are treated as a single slash '/'.
  • Any sequence of periods that does not match the rules above should be treated as a valid directory or file name. For example, '...' and '....' are valid directory or file names.

The simplified canonical path should follow these rules:

  • The path must start with a single slash '/'.
  • Directories within the path must be separated by exactly one slash '/'.
  • The path must not end with a slash '/', unless it is the root directory.
  • The path must not have any single or double periods ('.' and '..') used to denote current or parent directories.

Return the simplified canonical path.

 

Example 1:

Input: path = "/home/"

Output: "/home"

Explanation:

The trailing slash should be removed.

Example 2:

Input: path = "/home//foo/"

Output: "/home/foo"

Explanation:

Multiple consecutive slashes are replaced by a single one.

Example 3:

Input: path = "/home/user/Documents/../Pictures"

Output: "/home/user/Pictures"

Explanation:

A double period ".." refers to the directory up a level (the parent directory).

Example 4:

Input: path = "/../"

Output: "/"

Explanation:

Going one level up from the root directory is not possible.

Example 5:

Input: path = "/.../a/../b/c/../d/./"

Output: "/.../b/d"

Explanation:

"..." is a valid name for a directory in this problem.

 

Constraints:

  • 1 <= path.length <= 3000
  • path consists of English letters, digits, period '.', slash '/' or '_'.
  • path is a valid absolute Unix path.

Solutions

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
class Solution:
    def simplifyPath(self, path: str) -> str:
        stack = []
        for s in path.split("/"):
            if not s or s == ".":
                continue
            if s == "..":
                if stack:
                    stack.pop()
            else:
                stack.append(s)
        return "/" + "/".join(stack)

Submission Stats:

  • Runtime: 1 ms (49.01%)
  • Memory: 18 MB (13.57%)