LeetCode开心刷题四十八天——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"

搞清规则是很重要的，简而言之，遇到.代表当前层，忽略。..上一层，把已经入栈清除，剩下的文字都是正常的路径，但是开始要有/，中间的/只能有一个
Python问题是，没有封装的类，对这个要自己实现，另外用Python函数实现对/的分割

class Solution(object):
    def simplifyPath(self,path):
        """
        :type path: str
        :rtype: str
        """
        # define stack
        stack=list()
        # split string
        path=[p for p in path.split(‘/‘) if p]
        for p in path:
            if p == ‘.‘:
                continue
            elif p == ‘..‘:
                if stack:
                    stack.pop()
            else:
                stack.append(p)
        return ‘/‘+‘/‘.join(stack)

Solu=Solution()
path="/a/./b/../../c/"
print(Solu.simplifyPath(path))

BONUS:

1.有可能会出现多个/的情况，直接用split划分，会导致出现空字符串，解决方法是，加上判断语句。在循环过程直接加到stack里

2.

Python join() 方法用于将序列中的元素以指定的字符连接生成一个新的字符串。

语法

join()方法语法：

str.join(sequence)