August 23, 2024
P13 - Run-length encoding of a list (direct solution).
Implement the so-called run-length encoding data compression method directly. I.e. don't use other methods you've written (like P09'spack); do all the work directly.
Example:
> p13:encodeDirect(['a', 'a', 'a', 'a', 'b', 'c', 'c', 'a', 'a', 'd', 'e', 'e', 'e', 'e']).
[[a,a,a,a],[b],[c,c],[a,a],[d],[e,e,e,e]]erlang
% Run-length encoding of a list (direct solution).
%
-module(p13).
-export([encodeDirect/1]).
encodeDirect([H | T]) ->
encodeDirect([], 0, [H |T], H).
encodeDirect(FinalAns, Counter, [CurrH | CurrT], Elem) when CurrH == Elem ->
encodeDirect(FinalAns, Counter + 1, CurrT, Elem);
encodeDirect(FinalAns, Counter, [CurrH | CurrT], Elem) ->
encodeDirect(FinalAns ++ [fill(Counter, Elem, [])], 0, [CurrH | CurrT], CurrH);
encodeDirect(FinalAns, Counter, [], Elem) ->
FinalAns ++ [fill(Counter, Elem, [])].
fill(0, _, Ls) ->
Ls;
fill(Value, Elem, Ls) ->
fill(Value - 1, Elem, [Elem | Ls]).
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