2390-removing-stars-from-a-string.rb

# frozen_string_literal: true

# 2390. Removing Stars From a String
# https://leetcode.com/problems/removing-stars-from-a-string/
# Medium

=begin

You are given a string s, which contains stars *.

In one operation, you can:

* Choose a star in s.
* Remove the closest non-star character to its left, as well as remove the star itself.

Return the string after all stars have been removed.

Note:

* The input will be generated such that the operation is always possible.
* It can be shown that the resulting string will always be unique.

### Example 1:
Input: s = "leet**cod*e"
Output: "lecoe"
Explanation: Performing the removals from left to right:
- The closest character to the 1st star is 't' in "leet**cod*e". s becomes "lee*cod*e".
- The closest character to the 2nd star is 'e' in "lee*cod*e". s becomes "lecod*e".
- The closest character to the 3rd star is 'd' in "lecod*e". s becomes "lecoe".
There are no more stars, so we return "lecoe".

### Example 2:
Input: s = "erase*****"
Output: ""
Explanation: The entire string is removed, so we return an empty string.

### Constraints:
* 1 <= s.length <= 105
* s consists of lowercase English letters and stars *.
* The operation above can be performed on s.

=end

# @param {String} s
# @return {String}
def remove_stars(s)
  r = []
  s.each_byte do
    _1 == 42 ? r.pop : r << _1
  end
  r.pack "c*"
end

# **************** #
#       TEST       #
# **************** #

require "test/unit"
class Test_remove_stars < Test::Unit::TestCase
  def test_
    assert_equal "lecoe", remove_stars("leet**cod*e")
    assert_equal "", remove_stars("erase*****")
  end
end