71. Simplify Path

class Solution {
    public String simplifyPath(String path) {
      Deque<String> stack = new LinkedList<>();
      Set<String> set = new HashSet<>(Arrays.asList("",".", ".."));
      for( String element: path.split("/")){
        if(!set.contains(element)){
          stack.push(element);
        }else if(element.equals("..") && !stack.isEmpty()){
          stack.pop();
        }
      }
      if (stack.isEmpty()){
          return "/";
      }
      
      String result = "";
      for(String element: stack){
        result = "/" + element + result;
      }
      return result;
    }
}

 

 

“..” Means go up a level, so delete the prev 

“.” Means do nothing 

“” Means do nothing 

 

 

First, we need to split the input by the splitter “/”

 

 

这种方式Arrays.asList 又见到了， 

Set<String> set = new HashSet<>(Arrays.asList("",".", ".."));

        

 

When we pop stack. Need to check if the stack is empty or not 

If it’s not empty , we pop

 

 

After done traversing the input, we need to return the things stored in the 

Stack

 

If the stack is empty, return “/”

 

 

If the stack is not empty, we format the things in the stack by the splitter “/”

 

 

加结果的时候是这样加的， 加上之前的

result = "/" + element + result;

 

 

 

 

 

 

 

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".

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