71. Simplify Path

逻辑

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.

分析

注意split with '\' 已经包含了'\\' '\\\'的情况，后面 直接跳过空。

‘。。’和 stack not empty不能同时判断。

class Solution:
    def simplifyPath(self, path: str) -> str:

        ls = path.split('/')
        res = []
        for i in ls:
            if i == '.' or i == '':
                continue
            elif i == '..':
                if res:
                    res.pop()
            else:
                res.append(i)
 
        
        return '/' + ('/').join(res)