given an absolute path for a file (unix-style), simplify it.
for example,
path = “/home/”, => “/home”
path = “/a/./b/../../c/”, => “/c”
click to show corner cases.
corner cases:
did you consider the case where path = “/../”?
in this case, you should return “/”.
another corner case is the path might contain multiple slashes ‘/’ together, such as “/home//foo/”.
in this case, you should ignore redundant slashes and return “/home/foo”.
这个题目重点就是要理解它的意思，如果是一个点 . 那就是当前路径，不管，如果是两个点 .. 那就是当前路径的上一个目录。这样我们用栈来表示的话，就是如下所示
明白这个之后就一目了然了，就是注意返回的时候如果是”/”或者”/../”这种情形就行。
另一种链表的做法