secret_word_finder.rb

class SecretWordFinder
  def initialize(alphabet, cryptic_string)
    raise ArgumentError, "Invalid characters in cryptic string" unless valid?(alphabet, cryptic_string)
    
    @alphabet       = alphabet
    @cryptic_string = cryptic_string
  end

  def self.find_secret_word(alphabet, cryptic_string)
    new(alphabet, cryptic_string).find_secret_word
  end

  def find_secret_word
    reassemble_string
  end

  private
    def valid?(alphabet, cryptic_string)
      cryptic_string.chars.all? { |char| alphabet.include?(char) }
    end

    def cryptic_characters
      @cryptic_string.chars
    end

    def sort_characters_by_count
      cryptic_characters.sort_by { |char| cryptic_characters.count(char) }
    end

    def sorted_unique_characters
      sort_characters_by_count.uniq
    end

    def sorted_unique_characters_reversed
      sorted_unique_characters.reverse
    end

    def reassemble_string
      sorted_unique_characters_reversed.join.split('_').first
    end
end

alphabet       = "abcdefghijklmnopqrstuvwxyz_"
cryptic_string = "hayjfltwmnlstaddvdkabpggxpcbmykiymbyphllzozvwjlkqrmaoxnsxqxjhvyrjykaddsoedcyitmevubhgelbmrtk_kxdizfgagidqvbvqrkhwscpenkdqatrcrhbucwmsv_qbygnjsydpr_mqftjviinseckyllydrbmsmyjaszwkdhnpjtk_awdokmpx_fzekzkttovqlfkqvwjbexvzwlnzaqwg_pqlorsmb_mavbuegnsvxptvbgcvairgdgsccac_ug_hbnkbu_svcbrjewiloukndywehdopjckulwwidrycoxsrpngacezescjtcutprmybxdivulcn_znajvbauio_jyahxxnyeyyznkoosgucjlzyqsptpbucirirywbpryjpktw_vl_unycyosq__alklnzv_qkpslqckzmuqbqfjiztsmskqdyxshhxkslvwx_bhaa_opivrqiandjfeyvowrnyysfaem_cgcvxuohpo__umqvbuqnrtcyijtrqsrfjpglsenwypljqixyjvkhogujuljtlowqghlwoonctrkcfwbzqqtqtmzef_elmbybryfiego_jknatrcrtecihdjsjzsytgpcomxkyduygnivcnq_gftnoc_tktdzuubehdjagd_caudrtgujkjzmhxdpvqsg_wyemsrvsdweyclxyhpqeeaphsyhahbbguogsuxsgtzaxktglhxg_xzeqjgmzhpmwfzwpufnrvdnkoyyrdqiwvxflndssbmanersenhltqtmvcmexdusczopalyxgqmopkedsvoszbu_sefquucivicerrnigkutzdojtnqtrfmocyjqs_b_eiqoncrudjccjnwhkjmmaanjsvkycryhxyyhimiebzoukiffcabhlujcwzfnhzlnhdvxyfxarcsqqjwgtbcugqftxrtqrspmpzczbrxpmrlqjqvqaylgvfhxezasdfrarlfxfrbofetptkljmztwvpwrswhmxhsny_bmlkxvyp_pendkcovvsfgkpjirrt_yhue_tgvkggz_shj_aldhfrvcfqxktkxyafaltwqzxoliocjitcikomih_mgygwvxvupgstjpfzbajdmjulbq_trsorfhfpulxnvdeoavcradzphqlngfi_on_kvllspucpxdamnws_ewgxalrlajoeaxxqqondjygfvqfa_ieuuemlozh_qyktxpypmmgou_izoroouiisnpsquplvapnqrmrecjilm_esnsz_steohcisskjioezirv_wlmoipuevrtwthybtrjqpuhuoacmnakhbikccacxb_eicdzwgwfmcdqet_fjum_zkbcokewropykow_cmfkpwuagxgxyfohejmxasb_lzxyzax_bgzjxsb_ollvzqwpyyndezpitwzdeeqthmrhqrhpzwxvdvliycsjiueoxrevkx_gjtpiowhpnit_rdwkocfxvivkfqkom_tjoimirz_ypyufouphocswbzfdprbiirfntvxtvytxgzwjaysxhptbenatxiaxwutrmiwbifqmpkwpmzmlkfzqnprskfsuvnphrbxysufcckssxwcbvapxbkfmum_meucimvshsawiucmimicnwnptynlghaeaaxtopadocumadecakteiw_ckczsvctsjwbaboqkzq_eouxfaiyexmf_iyrdjrkiuuudseoiuitxiyzwctiwgqwokiygfjzdbtimbpgfwypvtwkrgmcevfhqsekybgylzdvohlkwozsvxtkscuejhfjiwcummauh_lufqovxdwamlzfbr_uuquguwyplombdncgwaujpt_zsjziueozsblsxbjhgvzkuitdxaaxoxzm_akqgkulphkxdy_ttwrkxc_vmzqjelfiytessl_dxqitnlrocrmrmdcbudfxehd_wvxkjarnizentw_zoghv_iqjjgssfxeb_gbcu_ewymrelnpmpkteoibldnp_mtygdgauicswadrkagqeglugfa_fgv_oadajyqlsjjunvd_elotxznhrscujaljcqmm_ltlgdhazmzmppniqrs_ovmrioeouyrcuooso_mcuhfqvhtj_eoiomqsstpfrcmhxrrohkgyrdgeaamcbpghuduanwkuafuxbrvmpczqmwrzlur_fslnqbiew_nluucoyyn_yxviekfzmki_lqnijumpdbyptuvthgcvpkqshcs_abxwndxssacqxvbgcunoouhtlnkhlfefztckwntbomtralhdfvatdpyvojwgfjtrtwgwpdgbkh_wauyeda_aopit"
secret_word    = SecretWordFinder.find_secret_word(alphabet, cryptic_string)

puts secret_word