Data commit

Task/Huffman-coding/Picat/huffman-coding.picat

@@ -0,0 +1,49 @@
+go =>
+  huffman("this is an example for huffman encoding").
+
+huffman(LA) :-
+   LS=sort(LA),
+   packList(LS,PL),
+   PLS=sort(PL).remove_dups(),
+   build_tree(PLS, A),
+   coding(A, [], C),
+   SC=sort(C).remove_dups(),
+   println("Symbol\tWeight\tCode"),
+   foreach(SS in SC) print_code(SS) end.
+
+build_tree([[V1|R1], [V2|R2]|T], AF) :-
+   V = V1 + V2,
+   A = [V, [V1|R1], [V2|R2]],
+   (   T=[] -> AF=A ; NT=sort([A|T]), build_tree(NT, AF) ).
+
+coding([_A,FG,FD], Code, CF) :-
+   (   is_node(FG) ->  coding(FG, [0 | Code], C1)
+          ;  leaf_coding(FG, [0 | Code], C1) ),
+   (   is_node(FD) ->  coding(FD, [1 | Code], C2)
+          ;  leaf_coding(FD, [1 | Code], C2) ),
+   append(C1, C2, CF).
+
+leaf_coding([FG,FD], Code, CF) :-
+   CodeR = reverse(Code),
+   CF = [[FG, FD, CodeR]] .
+
+is_node([_V, _FG, _FD]).
+
+print_code([N, Car, Code]) :-
+   printf("%w:\t%w\t", Car, N),
+   foreach(V in Code) print(V) end,
+   nl.
+
+packList([], []).
+packList([X],[[1,X]]).
+packList([X|Rest], XRunPacked) :-
+   XRunPacked = [XRun|Packed],
+   run(X, Rest, XRun, RRest),
+   packList(RRest, Packed).
+
+run(V, [], VV, [])  :- VV=[1,V].
+run(V, [V|LRest], [N1,V], RRest) :-
+   run(V, LRest, [N, V], RRest),
+   N1 = N + 1.
+run(V, [Other|RRest], [1,V], [Other|RRest]) :-
+   different_terms(V, Other).