[LeetCode] 588. Design In-Memory File System

Design a data structure that simulates an in-memory file system.

Implement the FileSystem class:

• FileSystem() Initializes the object of the system.
• List<String> ls(String path)
  • If path is a file path, returns a list that only contains this file's name.
  • If path is a directory path, returns the list of file and directory names in this directory.
  The answer should in lexicographic order.
• void mkdir(String path) Makes a new directory according to the given path. The given directory path does not exist. If the middle directories in the path do not exist, you should create them as well.
• void addContentToFile(String filePath, String content)
  • If filePath does not exist, creates that file containing given content.
  • If filePath already exists, appends the given content to original content.
• String readContentFromFile(String filePath) Returns the content in the file at filePath.

Example 1:

Input
["FileSystem", "ls", "mkdir", "addContentToFile", "ls", "readContentFromFile"]
[[], ["/"], ["/a/b/c"], ["/a/b/c/d", "hello"], ["/"], ["/a/b/c/d"]]
Output
[null, [], null, null, ["a"], "hello"]

Explanation
FileSystem fileSystem = new FileSystem();
fileSystem.ls("/");                         // return []
fileSystem.mkdir("/a/b/c");
fileSystem.addContentToFile("/a/b/c/d", "hello");
fileSystem.ls("/");                         // return ["a"]
fileSystem.readContentFromFile("/a/b/c/d"); // return "hello"

Constraints:

• 1 <= path.length, filePath.length <= 100
• path and filePath are absolute paths which begin with '/' and do not end with '/' except that the path is just "/".
• You can assume that all directory names and file names only contain lowercase letters, and the same names will not exist in the same directory.
• You can assume that all operations will be passed valid parameters, and users will not attempt to retrieve file content or list a directory or file that does not exist.
• 1 <= content.length <= 50
• At most 300 calls will be made to ls, mkdir, addContentToFile, and readContentFromFile.

设计内存文件系统。

Java实现

 1 class FileSystem {
 2     private class FileNode {
 3         private TreeMap<String, FileNode> children;
 4         private StringBuilder file;
 5         private String name;
 6 
 7         public FileNode(String name) {
 8             children = new TreeMap<>();
 9             file = new StringBuilder();
10             this.name = name;
11         }
12 
13         public String getContent() {
14             return file.toString();
15         }
16 
17         public String getName() {
18             return name;
19         }
20 
21         public void addContent(String content) {
22             file.append(content);
23         }
24 
25         public boolean isFile() {
26             return file.length() > 0;
27         }
28 
29         public List<String> getList() {
30             List<String> list = new ArrayList<>();
31             if (isFile()) {
32                 list.add(getName());
33             } else {
34                 list.addAll(children.keySet());
35             }
36             return list;
37         }
38     }
39 
40     private FileNode root;
41     
42     public FileSystem() {
43         root = new FileNode("");
44     }
45     
46     public List<String> ls(String path) {
47         return findNode(path).getList();
48     }
49     
50     public void mkdir(String path) {
51         findNode(path);
52     }
53     
54     public void addContentToFile(String filePath, String content) {
55         findNode(filePath).addContent(content);
56     }
57     
58     public String readContentFromFile(String filePath) {
59         return findNode(filePath).getContent();
60     }
61 
62     private FileNode findNode(String path) {
63         String[] files = path.split("/");
64         FileNode cur = root;
65         for (String file : files) {
66             if (file.length() == 0) {
67                 continue;
68             }
69             cur.children.putIfAbsent(file, new FileNode(file));
70             cur = cur.children.get(file);
71             if (cur.isFile()) {
72                 break;
73             }
74         }
75         return cur;
76     }
77 }
78 
79 /**
80  * Your FileSystem object will be instantiated and called as such:
81  * FileSystem obj = new FileSystem();
82  * List<String> param_1 = obj.ls(path);
83  * obj.mkdir(path);
84  * obj.addContentToFile(filePath,content);
85  * String param_4 = obj.readContentFromFile(filePath);
86  */

LeetCode 题目总结

标签：String,filePath,System,588,content,Design,file,path,public
来源： https://www.cnblogs.com/cnoodle/p/16513790.html