LeetCode 1598. 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.

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呃，这题看起来很吓人，但着实没什么难度也没什么算法技巧……虽然是个stack的tag但是感觉根本用不上stack啊。

有一个corner case需要注意，就是返回到根目录以后，如果还接着../的话其实还在根目录。

class Solution {
    public int minOperations(String[] logs) {
        int depth = 0;
        for (String s : logs) {
            if (s.equals("../")) {
                if (depth > 0) {
                    depth--;
                }
            } else if (s.equals("./")) {
                continue;
            } else {
                depth++;
            }
        }
        return depth;
    }
}