Crawler Log Folder Python Solution with Tests

Tested Python solution for LeetCode 1598 with 18 pytest cases. Generate a practice environment with lcpy.

LeetCode 1598, Easy. Topics: Array, String, Stack. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 18 parametrized pytest cases, and a playground notebook:

lcpy gen -n 1598   # by problem number
lcpy gen -s crawler_log_folder   # by problem name

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Problem

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.

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Examples

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

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

Input: logs = ["d1/","../","../","../"]
Output: 0

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Constraints

• 1 <= logs.length <= 10^3
• 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.

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Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

class Solution:
    # Time: O(n)
    # Space: O(1)
    def min_operations(self, logs: list[str]) -> int:
        depth = 0
        for op in logs:
            if op == "../":
                depth = max(0, depth - 1)
            elif op != "./":
                depth += 1
        return depth

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Complexity

Time	Space
O(n)	O(1)

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Tags

NeetCode All.