Narcissistic decimal number: Difference between revisions
→{{header|Prolog}}
Line 4,085:
</pre>
=={{header|Prolog}}==
works with swi-prolog
<syntaxhighlight lang="prolog">
digits(0, []):-!.
digits(N, [D|DList]):-
divmod(N, 10, N1, D),
digits(N1, DList).
combi(0, _, []).
combi(N, [X|T], [X|Comb]):-
N > 0,
N1 is N - 1,
combi(N1, [X|T], Comb).
combi(N, [_|T], Comb):-
N > 0,
combi(N, T, Comb).
powSum([], _, Sum, Sum).
powSum([D|DList], Pow, Acc, Sum):-
Acc1 is Acc + D^Pow,
powSum(DList, Pow, Acc1, Sum).
armstrong(Exp, PSum):-
numlist(0, 9, DigList),
(Exp > 1 ->
Min is 10^(Exp - 1)
; Min is 0
),
Max is 10^Exp,
combi(Exp, DigList, Comb),
powSum(Comb, Exp, 0, PSum),
between(Min, Max, PSum),
digits(PSum, DList),
sort(0, @=<, DList, DSort), % hold equal digits
( PSum =:= 0, Comb = [0] -> % special case because
true % DList in digits(0, DList) is [] and not [0]
; DSort = Comb
).
do:-between(1, 7, Exp),
findall(ArmNum, armstrong(Exp, ArmNum), ATemp),
sort(ATemp, AList),
writef('%d -> %w\n', [Exp, AList]),
fail.
do.
</syntaxhighlight>
| |||