Create 1233_Remove_Sub-Folders_from_the_Filesystem.md

Author: koji

1233_Remove_Sub-Folders_from_the_Filesystem.md

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+## 1233. Remove Sub-Folders from the Filesystem
+
+
+```
+Given a list of folders, remove all sub-folders in those folders and return in any order the folders after removing.
+
+If a folder[i] is located within another folder[j], it is called a sub-folder of it.
+
+The format of a path is one or more concatenated strings of the form: / followed by one or more lowercase English letters. For example, /leetcode and /leetcode/problems are valid paths while an empty string and / are not.
+
+ 
+
+Example 1:
+
+Input: folder = ["/a","/a/b","/c/d","/c/d/e","/c/f"]
+Output: ["/a","/c/d","/c/f"]
+Explanation: Folders "/a/b/" is a subfolder of "/a" and "/c/d/e" is inside of folder "/c/d" in our filesystem.
+Example 2:
+
+Input: folder = ["/a","/a/b/c","/a/b/d"]
+Output: ["/a"]
+Explanation: Folders "/a/b/c" and "/a/b/d/" will be removed because they are subfolders of "/a".
+Example 3:
+
+Input: folder = ["/a/b/c","/a/b/ca","/a/b/d"]
+Output: ["/a/b/c","/a/b/ca","/a/b/d"]
+ 
+
+Constraints:
+
+1 <= folder.length <= 4 * 10^4
+2 <= folder[i].length <= 100
+folder[i] contains only lowercase letters and '/'
+folder[i] always starts with character '/'
+Each folder name is unique.
+```
+
+```python
+class Solution:
+ def removeSubfolders(self, folder: List[str]) -> List[str]:
+ # sort folder
+ sorted_folder = sorted(folder)
+ folder_set = set()
+ 
+ for f in sorted_folder:
+ # n = len(f)
+ exist = False
+ for i,c in enumerate(f):
+ if c == '/':
+ if f[:i] in folder_set:
+ exist = True
+ break
+ 
+ if not exist:
+ folder_set.add(f)
+ 
+ return folder_set
+```
+
+
+```
+Runtime: 408 ms, faster than 28.41% of Python3 online submissions for Remove Sub-Folders from the Filesystem.
+Memory Usage: 30.3 MB, less than 34.29% of Python3 online submissions for Remove Sub-Folders from the Filesystem.
+```