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"title": "Delete Duplicate Folders in System",
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"content": "<p>Due to a bug, there are many duplicate folders in a file system. You are given a 2D array <code>paths</code>, where <code>paths[i]</code> is an array representing an absolute path to the <code>i<sup>th</sup></code> folder in the file system.</p>\n\n<ul>\n\t<li>For example, <code>["one", "two", "three"]</code> represents the path <code>"/one/two/three"</code>.</li>\n</ul>\n\n<p>Two folders (not necessarily on the same level) are <strong>identical</strong> if they contain the <strong>same non-empty</strong> set of identical subfolders and underlying subfolder structure. The folders <strong>do not</strong> need to be at the root level to be identical. If two or more folders are <strong>identical</strong>, then <strong>mark</strong> the folders as well as all their subfolders.</p>\n\n<ul>\n\t<li>For example, folders <code>"/a"</code> and <code>"/b"</code> in the file structure below are identical. They (as well as their subfolders) should <strong>all</strong> be marked:\n\n\t<ul>\n\t\t<li><code>/a</code></li>\n\t\t<li><code>/a/x</code></li>\n\t\t<li><code>/a/x/y</code></li>\n\t\t<li><code>/a/z</code></li>\n\t\t<li><code>/b</code></li>\n\t\t<li><code>/b/x</code></li>\n\t\t<li><code>/b/x/y</code></li>\n\t\t<li><code>/b/z</code></li>\n\t</ul>\n\t</li>\n\t<li>However, if the file structure also included the path <code>"/b/w"</code>, then the folders <code>"/a"</code> and <code>"/b"</code> would not be identical. Note that <code>"/a/x"</code> and <code>"/b/x"</code> would still be considered identical even with the added folder.</li>\n</ul>\n\n<p>Once all the identical folders and their subfolders have been marked, the file system will <strong>delete</strong> all of them. The file system only runs the deletion once, so any folders that become identical after the initial deletion are not deleted.</p>\n\n<p>Return <em>the 2D array </em><code>ans</code> <em>containing the paths of the <strong>remaining</strong> folders after deleting all the marked folders. The paths may be returned in <strong>any</strong> order</em>.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2021/07/19/lc-dupfolder1.jpg\" style=\"width: 200px; height: 218px;\" />\n<pre>\n<strong>Input:</strong> paths = [["a"],["c"],["d"],["a","b"],["c","b"],["d","a"]]\n<strong>Output:</strong> [["d"],["d","a"]]\n<strong>Explanation:</strong> The file structure is as shown.\nFolders "/a" and "/c" (and their subfolders) are marked for deletion because they both contain an empty\nfolder named "b".\n</pre>\n\n<p><strong>Example 2:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2021/07/19/lc-dupfolder2.jpg\" style=\"width: 200px; height: 355px;\" />\n<pre>\n<strong>Input:</strong> paths = [["a"],["c"],["a","b"],["c","b"],["a","b","x"],["a","b","x","y"],["w"],["w","y"]]\n<strong>Output:</strong> [["c"],["c","b"],["a"],["a","b"]]\n<strong>Explanation: </strong>The file structure is as shown. \nFolders "/a/b/x" and "/w" (and their subfolders) are marked for deletion because they both contain an empty folder named "y".\nNote that folders "/a" and "/c" are identical after the deletion, but they are not deleted because they were not marked beforehand.\n</pre>\n\n<p><strong>Example 3:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2021/07/19/lc-dupfolder3.jpg\" style=\"width: 200px; height: 201px;\" />\n<pre>\n<strong>Input:</strong> paths = [["a","b"],["c","d"],["c"],["a"]]\n<strong>Output:</strong> [["c"],["c","d"],["a"],["a","b"]]\n<strong>Explanation:</strong> All folders are unique in the file system.\nNote that the returned array can be in a different order as the order does not matter.\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= paths.length <= 2 * 10<sup>4</sup></code></li>\n\t<li><code>1 <= paths[i].length <= 500</code></li>\n\t<li><code>1 <= paths[i][j].length <= 10</code></li>\n\t<li><code>1 <= sum(paths[i][j].length) <= 2 * 10<sup>5</sup></code></li>\n\t<li><code>path[i][j]</code> consists of lowercase English letters.</li>\n\t<li>No two paths lead to the same folder.</li>\n\t<li>For any folder not at the root level, its parent folder will also be in the input.</li>\n</ul>\n",
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"hints": [
"Can we use a trie to build the folder structure?",
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