71. Simplify Path (Python)

Related Topic

Stack.

Description

Given an absolute path for a file (Unix-style), simplify it. Or in other words, convert it to the canonical path.

In a UNIX-style file system, a period . refers to the current directory. Furthermore, a double period .. moves the directory up a level.

Note that the returned canonical path must always begin with a slash /, and there must be only a single slash / between two directory names. The last directory name (if it exists) must not end with a trailing /. Also, the canonical path must be the shortest string representing the absolute path.

Sample I/O

Example 1

Input: "/home/"
Output: "/home"
Explanation: Note that there is no trailing slash after the last directory name.

Example 2

Input: "/../"
Output: "/"
Explanation: Going one level up from the root directory is a no-op, as the root level is the highest level you can go.

Example 3

Input: "/home//foo/"
Output: "/home/foo"
Explanation: In the canonical path, multiple consecutive slashes are replaced by a single one.

Example 4

Input: "/a/./b/../../c/"
Output: "/c"

Example 5

Input: "/a/../../b/../c//.//"
Output: "/c"

Methodology

This is straight forward question. We use stack to append and pop.

def simplifyPath(self, path: str) -> str:
    path=path.split('/')
    res = ""
    res_stack = []
    for index, char in enumerate(path):
        if char == "..":
            if res_stack:
                res_stack.pop()
        elif char == "." or char == "":
            pass
        else:
            res_stack.append('/'+char)
    if len(res_stack) == 0: return "/"
    return res.join(res_stack)

BigO

The split give O(n) and iterate path will cost O(n) and join will cost O(n) so in total is O(3n)