1233. Remove Sub-Folders from the Filesystem (#186)

Author: remy727

README.md

@@ -339,6 +339,7 @@
 | 1218 | Longest Arithmetic Subsequence of Given Difference | [Ruby](./algorithms/ruby/1218-longest-arithmetic-subsequence-of-given-difference.rb) | Medium |
 | 1220 | Count Vowels Permutation | [Ruby](./algorithms/ruby/1220-count-vowels-permutation.rb) | Hard |
 | 1232 | Check If It Is a Straight Line | [Ruby](./algorithms/ruby/1232-check-if-it-is-a-straight-line.rb) | Easy |
+| 1233 | Remove Sub-Folders from the Filesystem | [Ruby](./algorithms/ruby/1233-remove-sub-folders-from-the-filesystem.rb) | Medium |
 | 1239 | Maximum Length of a Concatenated String with Unique Characters | [Ruby](./algorithms/ruby/1239-maximum-length-of-a-concatenated-string-with-unique-characters.rb) | Medium |
 | 1254 | Number of Closed Islands | [Ruby](./algorithms/ruby/1254-number-of-closed-islands.rb) | Medium |
 | 1266 | Minimum Time Visiting All Points | [Ruby](./algorithms/ruby/1266-minimum-time-visiting-all-points.rb) | Easy |

algorithms/ruby/1233-remove-sub-folders-from-the-filesystem.rb

@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+# 1233. Remove Sub-Folders from the Filesystem
+# Medium
+# https://leetcode.com/problems/remove-sub-folders-from-the-filesystem
+
+=begin
+Given a list of folders folder, return the folders after removing all sub-folders in those folders. You may return the answer in any order.
+If a folder[i] is located within another folder[j], it is called a sub-folder of it. A sub-folder of folder[j] must start with folder[j], followed by a "/". For example, "/a/b" is a sub-folder of "/a", but "/b" is not a sub-folder of "/a/b/c".
+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 * 104
+* 2 <= folder[i].length <= 100
+* folder[i] contains only lowercase letters and '/'.
+* folder[i] always starts with the character '/'.
+* Each folder name is unique.
+=end
+
+# @param {String[]} folder
+# @return {String[]}
+def remove_subfolders(folder)
+  folder.sort!
+
+  ans = [folder[0]]
+
+  (1...folder.length).each do |i|
+    last_folder = ans[-1] + "/"
+
+    if !folder[i].start_with?(last_folder)
+      ans << folder[i]
+    end
+  end
+
+  ans
+end
+
+# **************** #
+#       TEST       #
+# **************** #
+
+require "test/unit"
+class Test_remove_subfolders < Test::Unit::TestCase
+  def test_
+    assert_equal ["/a", "/c/d", "/c/f"], remove_subfolders(["/a", "/a/b", "/c/d", "/c/d/e", "/c/f"])
+    assert_equal ["/a"], remove_subfolders(["/a", "/a/b/c", "/a/b/d"])
+    assert_equal ["/a/b/c", "/a/b/ca", "/a/b/d"], remove_subfolders(["/a/b/c", "/a/b/ca", "/a/b/d"])
+  end
+end