71. Simplify Path

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. For more information, see: Absolute path vs relative path in Linux/Unix

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.

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"

Example 6:

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

Firstly

先将路径切割成一个个单词
根据栈的规律，判断是否是..或者.进行筛选，然后拼接

class Solution(object):
    def simplifyPath(self, path):
        """
        :type path: str
        :rtype: str
        """
        path_lst = [s for s in path.split('/') if s.strip()]
        stack = []
        for s in path_lst:
            if s == '.':
                continue
            if s == '..':
                if stack:
                    stack.pop()
            else:
                stack.append(s)
        return '/' + '/'.join(stack)

Fastest

思想一样

class Solution(object):
    def simplifyPath(self, path):
        """
        :type path: str
        :rtype: str
        """
        stack = []
        for item in path.split('/'):
            if not item: continue
            if item=='..': 
                if stack: stack.pop()
            elif item != '.': stack.append(item)
        return '/'+'/'.join(stack)