Data commit

Task/Run-length-encoding/Erlang/run-length-encoding-1.erl

@@ -0,0 +1,46 @@
+-module(rle).
+
+-export([encode/1,decode/1]).
+
+-include_lib("eunit/include/eunit.hrl").
+
+encode(S) ->
+    doEncode(string:substr(S, 2), string:substr(S, 1, 1), 1, []).
+
+doEncode([], CurrChar, Count, R) ->
+    R ++ integer_to_list(Count) ++ CurrChar;
+doEncode(S, CurrChar, Count, R) ->
+    NextChar = string:substr(S, 1, 1),
+    if
+        NextChar == CurrChar ->
+            doEncode(string:substr(S, 2), CurrChar, Count + 1, R);
+        true ->
+            doEncode(string:substr(S, 2), NextChar, 1,
+                R ++ integer_to_list(Count) ++ CurrChar)
+    end.
+
+decode(S) ->
+    doDecode(string:substr(S, 2), string:substr(S, 1, 1), []).
+
+doDecode([], _, R) ->
+    R;
+doDecode(S, CurrString, R) ->
+    NextChar = string:substr(S, 1, 1),
+    IsInt = erlang:is_integer(catch(erlang:list_to_integer(NextChar))),
+    if
+        IsInt ->
+            doDecode(string:substr(S, 2), CurrString ++ NextChar, R);
+        true ->
+            doDecode(string:substr(S, 2), [],
+                R ++ string:copies(NextChar, list_to_integer(CurrString)))
+    end.
+
+rle_test_() ->
+    PreEncoded =
+        "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW",
+    Expected = "12W1B12W3B24W1B14W",
+    [
+        ?_assert(encode(PreEncoded) =:= Expected),
+        ?_assert(decode(Expected) =:= PreEncoded),
+        ?_assert(decode(encode(PreEncoded)) =:= PreEncoded)
+    ].

Task/Run-length-encoding/Erlang/run-length-encoding-2.erl

@@ -0,0 +1,20 @@
+-module(rle).
+
+-export([encode/1, decode/1]).
+
+encode(L) -> encode(L, []).
+encode([], Acc) -> {rle, lists:reverse(Acc)};
+encode([H|T], []) ->
+    encode(T, [{1, H}]);
+encode([H|T], [{Count, Char}|AT]) ->
+    if
+        H =:= Char ->
+            encode(T, [{Count + 1, Char}|AT]);
+        true ->
+            encode(T, [{1, H}|[{Count, Char}|AT]])
+    end.
+
+decode({rle, L}) -> lists:append(lists:reverse(decode(L, []))).
+decode([], Acc) -> Acc;
+decode([{Count, Char}|T], Acc) ->
+    decode(T, [[Char || _ <- lists:seq(1, Count)]|Acc]).