71. Simplify Path

Given an absolute path for a file (Unix-style), simplify it.

Have you met this question in a real interview? 
Yes
Example

"/home/", => "/home"

"/a/./b/../../c/", => "/c"

Challenge 

  • 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".

 1 class Solution {
 2      /* 归下类的话，有四种字符串：
 3         1. "/"：为目录分隔符，用来分隔两个目录。
 4         2. "."：当前目录
 5         3. ".."：上层目录
 6         4. 其他字符串：目录名
 7 
 8         简化的核心是要找出所有的目录，并且如果遇到".."，需要删除上一个目录。
 9      */
10         public  String simplifyPath(String path) {
11         if (path == null || path.length() == 0) return path;
12 
13         String[] subPath = path.split("/");
14         Stack<String> stack = new Stack<>();
15         for (int i = 0; i < subPath.length; i++) {
16             String str = subPath[i];
17             if (!(str.equals(".") || str.isEmpty())) { // for . and empty string, we do nothing.
18                 if (str.equals("..")) { // we need to remove one upper directory
19                     if (!stack.isEmpty()) {
20                         stack.pop();
21                     }
22                 } else {
23                     stack.push("/" + str);
24                 }
25             }
26         }
27         
28         StringBuilder sb = new StringBuilder();
29         for (String str : stack) {
30             sb.append(str);
31         }
32         return sb.length() == 0 ? "/" : sb.toString();
33     }
34 
35 }

Use StringBuilder

 1 public class Solution {
 2         public static String simplifyPath(String path) {
 3         if (path == null || path.length() == 0) return path;
 4 
 5         String[] subPath = path.split("/");
 6         StringBuilder sb = new StringBuilder("");
 7         for (int i = 0; i < subPath.length; i++) {
 8             String str = subPath[i];
 9             if (!(str.equals(".") || str.isEmpty())) { // for . and empty string, we do nothing.
10                 if (str.equals("..")) { // we need to remove one upper directory
11                     if (sb.length() > 1) {
12                         int k = sb.length() - 1;
13                         while (sb.length() >= 1 && sb.charAt(k) != '/') {
14                             sb.deleteCharAt(k);
15                             k--;
16                         }
17                         sb.deleteCharAt(k); // "delete the last /"
18                     }
19                 } else {
20                     sb.append("/");
21                     sb.append(str);
22                 }
23             }
24         }
25         if (sb.length() == 0) {
26             return "/";
27         }
28         return sb.toString();
29     }
30 }

 

 

posted @ 2016-07-17 01:02  北叶青藤  阅读(216)  评论(0)  编辑  收藏  举报