public class Solution
extends Object
1598 - Crawler Log Folder\.
Easy
The Leetcode file system keeps a log each time some user performs a _change folder_ operation.
The operations are described below:
* `"../"` : Move to the parent folder of the current folder. (If you are already in the main folder, **remain in the same folder** ).
* `"./"` : Remain in the same folder.
* `"x/"` : Move to the child folder named `x` (This folder is **guaranteed to always exist** ).
You are given a list of strings `logs` where `logs[i]` is the operation performed by the user at the ith step.
The file system starts in the main folder, then the operations in `logs` are performed.
Return _the minimum number of operations needed to go back to the main folder after the change folder operations._
**Example 1:**
**Input:** logs = ["d1/","d2/","../","d21/","./"]
**Output:** 2
**Explanation:** Use this change folder operation "../" 2 times and go back to the main folder.
**Example 2:**
**Input:** logs = ["d1/","d2/","./","d3/","../","d31/"]
**Output:** 3
**Example 3:**
**Input:** logs = ["d1/","../","../","../"]
**Output:** 0
**Constraints:**
* 1 <= logs.length <= 103
* `2 <= logs[i].length <= 10`
* `logs[i]` contains lowercase English letters, digits, `'.'`, and `'/'`.
* `logs[i]` follows the format described in the statement.
* Folder names consist of lowercase English letters and digits.