LeetCode 1598. Folder operation log collector

1598. Folder operations log collector

Whenever a user performs a change folder operation ,LeetCode The file system keeps a log record .

The following is a description of the change operation ：

• "../" ： Move to the parent folder of the current folder . If it is already in the home folder , be Continue to stay in the current folder .
• "./" ： Continue to stay in the current folder **.**
• "x/" ： Move to a place called x In subfolders of . Subject data The folder always exists x .

Here's a list of strings logs , among logs[i] It's the user ith What to do next .

The file system starts in the home folder , And then execute logs The operation .

After all folder changes have been performed , Please find out The minimum number of steps required to return to the home folder .

Example 1：

 Input ：logs = ["d1/","d2/","../","d21/","./"]
 Output ：2
 explain ： perform  "../"  Operation change folder  2  Time , You can go back to your home folder 

Example 2：

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

Example 3：

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

Tips ：

• 1 <= logs.length <= 103
• 2 <= logs[i].length <= 10
• logs[i] Contains lowercase English letters , Numbers ,'.' and '/'
• logs[i] Conform to the format described in the statement
• The folder name consists of lowercase English letters and numbers

Two 、 Method 1

class Solution {
    
    public int minOperations(String[] logs) {
    
        int ans = 0;
        for (String log : logs) {
    
            if (log.charAt(0) != '.') ans++;
            else if (ans != 0 && log.equals("../")) ans--;
        }
        return ans;
    }
}

Complexity analysis

• Time complexity ：O(n).

• Spatial complexity ：O(1).