Kaprekar numbers: Difference between revisions
Added Erlang version
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(Added Erlang version) |
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83520 GGGG GGGF0001 GGGF + 0001
266224 33334 A2C52A07G A2C5 + 2A07G</pre>
=={{header|Erlang}}==
<lang Erlang>
-mode(compile).
-import(lists, [seq/2]).
kaprekar(1) -> true;
kaprekar(N) when N < 1 -> false;
kaprekar(N) ->
Sq = N*N,
if
(N rem 9) =/= (Sq rem 9) -> false;
true -> kaprekar(N, Sq, 10)
end.
kaprekar(_, Sq, M) when (Sq div M) =:= 0 -> false;
kaprekar(N, Sq, M) ->
L = Sq div M,
R = Sq rem M,
if
R =/= 0 andalso (L + R) =:= N -> true;
true -> kaprekar(N, Sq, M * 10)
end.
main(_) ->
Numbers = [N || N <- seq(1, 9999), kaprekar(N)],
io:format("The Kaprekar numbers < 10,000 are ~p~n", [Numbers]),
CountTo1e6 = length(Numbers) + length([N || N <- seq(10001, 999999), kaprekar(N)]),
io:format("There are ~p Kaprekar numbers < 1,000,000", [CountTo1e6]).
</lang>
{{out}}
<pre>
The Kaprekar numbers < 10,000 are [1,9,45,55,99,297,703,999,2223,2728,4879,
4950,5050,5292,7272,7777,9999]
There are 54 Kaprekar numbers < 1,000,000
</pre>
=={{header|Euler Math Toolbox}}==
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