Add a function to get the ordered sequence that can form a key.

src/cipher_analytical_machine/analyzers/analyzers.clj

@@ -11,6 +11,16 @@
             (inc (get acc val 0))))
    {} text))
 
+(defn reverse-count-characters
+  "Convert a map of pairs to a map where the characters grouped by the count and a count is the key."
+  [count-map]
+  (reduce
+   (fn [acc [symbol count]]
+     (->> (conj (get acc count []) symbol)
+          (into [])
+          (assoc acc count)))
+   {} count-map))
+
 (defn chi-squared-letter-statistic
   "To calculate the frequency distribution of a letter."
   [letter-count letter-frequence length-text]

src/cipher_analytical_machine/analyzers/simple_substitution.clj

@@ -7,13 +7,22 @@
   (:gen-class))
 
 (defn get-possible-key-vector
-  "Conver a possible key map to a vector of possible keys. For example, if you have a map: {\\a [\\a \\b \\c] \\b [\\b \\c] \\c [\\a \\c]}, then the vector is [[\\a \\b \\c] [\\b \\c] [\\a \\c]]."
+  "Convert a possible key map to a vector of possible keys. For example, if you have a map: {\\a [\\a \\b \\c] \\b [\\b \\c] \\c [\\a \\c]}, then the vector is [[\\a \\b \\c] [\\b \\c] [\\a \\c]]."
   [possible-key-map symbols]
   (reduce
    (fn [acc el]
      (conj acc (get possible-key-map el)))
    [] symbols))
 
+(defn get-possible-key-vector-from-reversed-count-map
+  "Convert a reversed count map to a vector. Example, from {2 [\\a \\b] 1 [\\d] 3 [\\e]} to [[\\e] [\\a \\b] [\\d]])."
+  [reversed-count-map]
+  (->>  reversed-count-map
+        (into [])
+        (sort-by #(- (first %)))
+        (map second)
+        (into [])))
+
 (defn get-possible-keys
   "Return possible keys for a possible key vector. For example, if you have a map: {\\a [\\a \\b \\c] \\b [\\b \\c] \\c [\\a \\c]}, then the vector is [[\\a \\b \\c] [\\b \\c] [\\a \\c]] and keys (\"aba\" \"abc\" ...)."
   [possible-key-vector]

test/cipher_analytical_machine/analyzers/analyzers_test.clj

@@ -8,6 +8,13 @@
     (is (= {\a 2 \b 1}
            (count-characters "aba")))))
 
+(deftest reverse-count-characters-test
+  (testing "The symbols must be grouped as a vector and the count must be a key."
+    (are [count-map expected-map]
+        (= expected-map (reverse-count-characters count-map))
+      {\a 1 \b 2 \c 1} {1 [\a \c] 2 [\b]}
+      {\a 1 \b 2 \c 3} {1 [\a] 2 [\b] 3 [\c]})))
+
 (deftest chi-squared-letter-statistic-test
   (testing "If the frequence of A is 0.1, the text length is 100 and contains 20 times, then the chi-squared is 10."
     (is (= 10.0

test/cipher_analytical_machine/analyzers/simple_substitution_test.clj

@@ -13,6 +13,13 @@
       {\a [\a \b] \b [\b \a] \c [\a \c]} "abc" [[\a \b] [\b \a] [\a \c]]
       {\a [\a \b] \c [\b \a] \b [\a \c]} "abc" [[\a \b] [\a \c] [\b \a]])))
 
+(deftest get-possible-key-vector-from-reversed-count-map-test
+  (testing ""
+    (are [reversed-count-map expected-key-vector]
+        (= expected-key-vector (get-possible-key-vector-from-reversed-count-map reversed-count-map))
+      {1 [\a \c] 2 [\b]}     [[\b] [\a \c]]
+      {2 [\a] 1 [\b] 3 [\c]} [[\c] [\a] [\b]])))
+
 (deftest get-possible-keys-test
   (testing "The keys must be the all combinations"
     (are [possible-keys-vector expected-keys]