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 namedx
(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.
Solution: Simulation
We only need to track the depth of current folder, and name and path can be ignored.
Time complexity: O(n)
Space complexity: O(1)
C++
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// Author: Huahua class Solution { public: int minOperations(vector<string>& logs) { int ans = 0; for (const string& log : logs) { if (log == "../") ans = max(ans - 1, 0); else if (log != "./") ++ans; } return ans; } }; |
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