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.

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"

class Solution {
    public String simplifyPath(String path) {
        Stack<String> stack = new Stack<>();
        Set<String> skip = new HashSet<>(Arrays.asList("..", ".", ""));
        for (String dir : path.split("/")) {
            if (dir.equals("..") && !stack.isEmpty())
                stack.pop();
            else if (!skip.contains(dir))
                stack.push(dir);
        }
        String res = "";
        for (String dir : stack){
            res = res + "/" + dir;
        }
        return res.isEmpty() ? "/" : res;
    }
}