Crawler Log Folder

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.