1598.CrawlerLogFolder.py

"""
    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:
    Input: logs = ["d1/","d2/","../","d21/","./"]
    Output: 2
    Explanation: Use this change folder operation "../" 2 times and go back to 
                 the main folder.

    Example:
    Input: logs = ["d1/","d2/","./","d3/","../","d31/"]
    Output: 3

    Example:
    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.
"""
#Difficulty: Easy
#99 / 99 test cases passed.
#Runtime: 40 ms
#Memory Usage: 14.5 MB

#Runtime: 40 ms, faster than 94.98% of Python3 online submissions for Crawler Log Folder.
#Memory Usage: 14.5 MB, less than 8.78% of Python3 online submissions for Crawler Log Folder.

class Solution:
    def minOperations(self, logs: List[str]) -> int:
        steps = 0
        for log in logs:
            if log == '../':
                steps = max(steps - 1, 0)
            elif log == './':
                pass
            else:
                steps += 1
        return steps