leetcode/work/1/Medium/String/71.simplify-path.py

"""
71. Simplify Path
Difficulty: Medium
https://leetcode.com/problems/simplify-path/

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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.
"""


class Solution:
    def simplifyPath(self, path: str) -> str:
        stack = []
        segments = [item for item in path.split("/") if item]

        for p in segments:
            if stack and p == "..":
                stack.pop()
            elif not stack and p == ".." or p == ".":
                continue
            else:
                stack.append(p)

        return "/" + "/".join(stack)