longest-absolute-file-path

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Algorithms

Suppose we have a file system that stores both files and directories. An example of one system is represented in the following picture:

<img alt="" src="https://assets.leetcode.com/uploads/2020/08/28/mdir.jpg" style="width: 681px; height: 322px;" />

Here, we have <code>dir</code> as the only directory in the root. <code>dir</code> contains two subdirectories, <code>subdir1</code> and <code>subdir2</code>. <code>subdir1</code> contains a file <code>file1.ext</code> and subdirectory <code>subsubdir1</code>. <code>subdir2</code> contains a subdirectory <code>subsubdir2</code>, which contains a file <code>file2.ext</code>.

In text form, it looks like this (with ⟶ representing the tab character):

<pre>
dir
⟶ subdir1
⟶ ⟶ file1.ext
⟶ ⟶ subsubdir1
⟶ subdir2
⟶ ⟶ subsubdir2
⟶ ⟶ ⟶ file2.ext
</pre>

If we were to write this representation in code, it will look like this: <code>&quot;dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile2.ext&quot;</code>. Note that the <code>&#39;\n&#39;</code> and <code>&#39;\t&#39;</code> are the new-line and tab characters.

Every file and directory has a unique absolute path in the file system, which is the order of directories that must be opened to reach the file/directory itself, all concatenated by <code>&#39;/&#39;s</code>. Using the above example, the absolute path to <code>file2.ext</code> is <code>&quot;dir/subdir2/subsubdir2/file2.ext&quot;</code>. Each directory name consists of letters, digits, and/or spaces. Each file name is of the form <code>name.extension</code>, where <code>name</code> and <code>extension</code> consist of letters, digits, and/or spaces.

Given a string <code>input</code> representing the file system in the explained format, return the length of the longest absolute path to a file in the abstracted file system. If there is no file in the system, return <code>0</code>.

Note that the testcases are generated such that the file system is valid and no file or directory name has length 0.

&nbsp;
Example 1:
<img alt="" src="https://assets.leetcode.com/uploads/2020/08/28/dir1.jpg" style="width: 401px; height: 202px;" />
<pre>
Input: input = &quot;dir\n\tsubdir1\n\tsubdir2\n\t\tfile.ext&quot;
Output: 20
Explanation: We have only one file, and the absolute path is &quot;dir/subdir2/file.ext&quot; of length 20.
</pre>

Example 2:
<img alt="" src="https://assets.leetcode.com/uploads/2020/08/28/dir2.jpg" style="width: 641px; height: 322px;" />
<pre>
Input: input = &quot;dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile2.ext&quot;
Output: 32
Explanation: We have two files:
&quot;dir/subdir1/file1.ext&quot; of length 21
&quot;dir/subdir2/subsubdir2/file2.ext&quot; of length 32.
We return 32 since it is the longest absolute path to a file.
</pre>

Example 3:

<pre>
Input: input = &quot;a&quot;
Output: 0
Explanation: We do not have any files, just a single directory named &quot;a&quot;.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= input.length &lt;= 104</code></li>
	<li><code>input</code> may contain lowercase or uppercase English letters, a new line character <code>&#39;\n&#39;</code>, a tab character <code>&#39;\t&#39;</code>, a dot <code>&#39;.&#39;</code>, a space <code>&#39; &#39;</code>, and digits.</li>
	<li>All file and directory names have positive length.</li>
</ul>

lengthLongestPath

Longest Absolute File Path

Stack

Depth-First Search

String

假设有一个同时存储文件和目录的文件系统。下图展示了文件系统的一个示例：

<img alt="" src="https://assets.leetcode.com/uploads/2020/08/28/mdir.jpg" style="height: 142px; width: 300px;" />

这里将 <code>dir</code> 作为根目录中的唯一目录。<code>dir</code> 包含两个子目录 <code>subdir1</code> 和 <code>subdir2</code> 。<code>subdir1</code> 包含文件 <code>file1.ext</code> 和子目录 <code>subsubdir1</code>；<code>subdir2</code> 包含子目录 <code>subsubdir2</code>，该子目录下包含文件 <code>file2.ext</code> 。

在文本格式中，如下所示(⟶表示制表符)：

<pre>
dir
⟶ subdir1
⟶ ⟶ file1.ext
⟶ ⟶ subsubdir1
⟶ subdir2
⟶ ⟶ subsubdir2
⟶ ⟶ ⟶ file2.ext
</pre>

如果是代码表示，上面的文件系统可以写为 <code>"dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile2.ext"</code> 。<code>'\n'</code> 和 <code>'\t'</code> 分别是换行符和制表符。

文件系统中的每个文件和文件夹都有一个唯一的 绝对路径 ，即必须打开才能到达文件/目录所在位置的目录顺序，所有路径用 <code>'/'</code> 连接。上面例子中，指向 <code>file2.ext</code> 的 绝对路径 是 <code>"dir/subdir2/subsubdir2/file2.ext"</code> 。每个目录名由字母、数字和/或空格组成，每个文件名遵循 <code>name.extension</code> 的格式，其中<meta charset="UTF-8" />&nbsp;<code>name</code>&nbsp;和<meta charset="UTF-8" />&nbsp;<code>extension</code>由字母、数字和/或空格组成。

给定一个以上述格式表示文件系统的字符串 <code>input</code> ，返回文件系统中&nbsp;指向&nbsp;文件&nbsp;的 最长绝对路径 的长度&nbsp;。 如果系统中没有文件，返回&nbsp;<code>0</code>。

&nbsp;

示例 1：
<img alt="" src="https://assets.leetcode.com/uploads/2020/08/28/dir1.jpg" style="height: 101px; width: 200px;" />
<pre>
输入：input = "dir\n\tsubdir1\n\tsubdir2\n\t\tfile.ext"
输出：20
解释：只有一个文件，绝对路径为 "dir/subdir2/file.ext" ，路径长度 20
</pre>

示例 2：
<img alt="" src="https://assets.leetcode.com/uploads/2020/08/28/dir2.jpg" style="height: 151px; width: 300px;" />
<pre>
输入：input = "dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile2.ext"
输出：32
解释：存在两个文件：
"dir/subdir1/file1.ext" ，路径长度 21
"dir/subdir2/subsubdir2/file2.ext" ，路径长度 32
返回 32 ，因为这是最长的路径</pre>

示例 3：

<pre>
输入：input = "a"
输出：0
解释：不存在任何文件</pre>

示例 4：

<pre>
输入：input = "file1.txt\nfile2.txt\nlongfile.txt"
输出：12
解释：根目录下有 3 个文件。
因为根目录中任何东西的绝对路径只是名称本身，所以答案是 "longfile.txt" ，路径长度为 12
</pre>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= input.length &lt;= 104</code></li>
	<li><code>input</code> 可能包含小写或大写的英文字母，一个换行符 <code>'\n'</code>，一个制表符 <code>'\t'</code>，一个点 <code>'.'</code>，一个空格 <code>' '</code>，和数字。</li>
</ul>