1233-remove-sub-folders-from-the-filesystem.rb

# 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