【leetcode刷题笔记】Simplify Path

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

For example,
path = "/home/", => "/home"
path = "/a/./b/../../c/", => "/c"

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".

---

题解：

1. 用split函数将path按照一个或者多个（正则表达式实现）'/'分成不同的字符串存放在数组positions中。
2. 遍历positions，如果遇到非"..",".",""的字符串，就放入answers列表中；如果遇到".."且answers不为空，就把answers尾部的字符串扔掉。
3. 最后把answers中的字符串用"/"连接起来，注意在连接后的字符串结尾会多一个"/'，可以substring一下result去掉。

代码如下：

 public class Solution {

     public String simplifyPath(String path) {

         ArrayList<String> answers = new ArrayList<String>();

         String[] positions = path.split("/+");

         for(int i = 0;i < positions.length;i++){

             if(positions[i].equals("..")){

                 if(answers.size() > 0)

                     answers.remove(answers.size()-1);

             }

             else if(!positions[i].equals(".") && !positions[i].equals(""))

             {

                 answers.add(positions[i]);

             }

         }

         String result = new String("/");

         for(String s:answers)

             result += s + "/";

         if(result.length() > 1)

             result = result.substring(0,result.length()-1);

         return result;

     }

 }