Heap (Erlang)

From LiteratePrograms

Heap structure in Erlang

-module(heap).
-export([start/0]).
start() ->
	L=[7,1,3,4,0,5,5,8],
	heapify(L).
heapify(L)->
	heapify(L, []).
heapify([], Acc) ->
	Acc;
heapify([H|T], Acc)->
	K=Acc ++ [H],
	J=siftup(K),
	heapify(T, J).
siftup(M)->
	siftup(M, length(M)).
siftup(M, N) when N > 0->
	Ppos=trunc((N+1)/2),
	P=lists:nth(Ppos, M),
	Q=lists:nth(N, M),
	case N > 0 andalso Q > P of
		true ->
			{J, [_|Ta]}=lists:split(Ppos-1, M),
			Lx=J++[Q]++Ta,
			{K, [_|Tb]}=lists:split(N-1, Lx),
			Ly=K ++ [P] ++ Tb,
			siftup(Ly, Ppos);
		false ->
			M
		end;
siftup(M, _) ->
	M.

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