Add solution #588

Author: JoshCrozier

README.md

@@ -561,6 +561,7 @@
 582|[Kill Process](./solutions/0582-kill-process.js)|Medium|
 583|[Delete Operation for Two Strings](./solutions/0583-delete-operation-for-two-strings.js)|Medium|
 587|[Erect the Fence](./solutions/0587-erect-the-fence.js)|Hard|
+588|[Design In-Memory File System](./solutions/0588-design-in-memory-file-system.js)|Hard|
 589|[N-ary Tree Preorder Traversal](./solutions/0589-n-ary-tree-preorder-traversal.js)|Easy|
 590|[N-ary Tree Postorder Traversal](./solutions/0590-n-ary-tree-postorder-traversal.js)|Easy|
 591|[Tag Validator](./solutions/0591-tag-validator.js)|Hard|

solutions/0588-design-in-memory-file-system.js

@@ -0,0 +1,97 @@
+/**
+ * 588. Design In-Memory File System
+ * https://leetcode.com/problems/design-in-memory-file-system/
+ * Difficulty: Hard
+ *
+ * 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.
+ */
+
+var FileSystem = function() {
+  this.root = new Map();
+};
+
+/**
+ * @param {string} path
+ * @return {string[]}
+ */
+FileSystem.prototype.ls = function(path) {
+  const parts = path === '/' ? [] : path.split('/').slice(1);
+  let current = this.root;
+
+  for (const part of parts) {
+    current = current.get(part);
+  }
+
+  if (typeof current === 'string') {
+    return [parts[parts.length - 1]];
+  }
+
+  return Array.from(current.keys()).sort();
+};
+
+/**
+ * @param {string} path
+ * @return {void}
+ */
+FileSystem.prototype.mkdir = function(path) {
+  const parts = path.split('/').slice(1);
+  let current = this.root;
+
+  for (const part of parts) {
+    if (!current.has(part)) {
+      current.set(part, new Map());
+    }
+    current = current.get(part);
+  }
+};
+
+/**
+ * @param {string} filePath
+ * @param {string} content
+ * @return {void}
+ */
+FileSystem.prototype.addContentToFile = function(filePath, content) {
+  const parts = filePath.split('/').slice(1);
+  const fileName = parts.pop();
+  let current = this.root;
+
+  for (const part of parts) {
+    if (!current.has(part)) {
+      current.set(part, new Map());
+    }
+    current = current.get(part);
+  }
+
+  const existingContent = current.get(fileName) || '';
+  current.set(fileName, existingContent + content);
+};
+
+/**
+ * @param {string} filePath
+ * @return {string}
+ */
+FileSystem.prototype.readContentFromFile = function(filePath) {
+  const parts = filePath.split('/').slice(1);
+  const fileName = parts.pop();
+  let current = this.root;
+
+  for (const part of parts) {
+    current = current.get(part);
+  }
+
+  return current.get(fileName);
+};