71. Simplify Path

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".

这道题需要用到栈。遍历path，不是“..”，“.”，和“”就入栈，遇到“..”就弹栈，最后遍历栈，组成字符串。代码如下：

public class Solution {    public String simplifyPath(String path) {        Deque<String> stack = new LinkedList<>();        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 = "/" + dir + res;        }        return res.isEmpty()? "/": res;    }}