require "set"
# Removes all characters from source that appear
# in chars_to_remove.
def remove_characters(source, chars_to_remove)
forbidden = chars_to_remove.chars.to_set
source
.chars
.reject { |ch| forbidden.include?(ch) }
.join
end
first = "programming language"
second = "rogy"
result = remove_characters(second, first)
puts %(First : "#{first}")
puts %(Second: "#{second}")
puts %(Result: "#{result}")
# run:
#
# First : "programming language"
# Second: "rogy"
# Result: "y"
#