[LeetCode]Simplify Path

题目说明

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".

思路

本题就是对输入的字符串逐个处理的过程，但是要注意两个特殊情况，(1)如果在根目录下输入..，则仍在根目录，而不是跳到上级目录。(2)如果有两个分隔符在一块的话就当做一个分隔符处理。我们只要将输入字符串用”/”分割开来得到一个字符串数组，然后对这个数组内的元素依次处理即可。作者新建了一个Path类，该类包含了一个变量按顺序保存了所有到当前路径的目录名称，提供了一个方法对新输入的字符串进行处理，如果当前路径是根路径，遇到..就不做处理（情况1）。如果新来的字符串是”.”或者空（情况2）也不做处理。其他情况下遇到..删除最顶层目录。遇到普通目录新加一个目录。最后输出结果即可。

代码

import java.util.ArrayList;

class Path

{

   private ArrayList<String> paths=new ArrayList<>();

   public void ParseNewDir(String dir)

   {

   if(dir.equals("")||dir.equals(".")||(dir.equals("..")&&paths.size()==0))

      {

        return;

      }

      if(dir.equals(".."))

      {

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

      }

      else

      {

        paths.add(dir);

      }

   }

   public String GetFullDir()

   {

      if(paths.size()==0)

        return "/";

      StringBuilder sb=new StringBuilder();

      for(int i=0;i<paths.size();i++)

      {

        sb.append("/");

        sb.append(paths.get(i));

      }

      return sb.toString();

   }

}

public class Simplify_Path {

     public String simplifyPath(String path) {

           // Note: The Solution object is instantiated only once and is reused by each test case.

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

           Path fullDir=new Path();

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

           {

           String newDir=splits[i];

           fullDir.ParseNewDir(newDir);

           }

           return fullDir.GetFullDir();

       }

     public static void main(String[] args)

     {

        System.out.println(new Simplify_Path().simplifyPath("/../"));

     }

}