count_xox_games.sql

create or replace function is_done(g int[])
    returns boolean
as
$$
select exists(
               select
               from (
                        select array [g[1], g[3], g[5], g[7], g[9]]::int[] as moves
                        union all
                        select array [g[2], g[4], g[6], g[8]]::int[] as moves
                    ) z
               where (moves @> array [1,2,3])
                  or (moves @> array [4,5,6])
                  or (moves @> array [7,8,9])
                  or (moves @> array [1,4,7])
                  or (moves @> array [2,5,8])
                  or (moves @> array [3,6,9])
                  or (moves @> array [1,5,9])
                  or (moves @> array [3,5,7])
           );
$$ language sql;


create or replace function shorten_game(g int[])
    returns int[] as
$$
declare
    short int[];
begin

    if (not is_done(g))
    then
        return g;
    end if;

    short = g[0:array_length(g, 1) - 1];
    if (is_done(short))
    then
        return shorten_game(short);
    end if;

    return g;
end;
$$
    language plpgsql;

with gamefield as (
    select generate_series(1, 9) as id,
           pow(2, generate_series(0, 8)) as mask
),
     games as (
         select distinct shorten_game(
                                 array [g1.id, g2.id, g3.id, g4.id, g5.id, g6.id, g7.id, g8.id, g9.id]::int[]) as moves
         from gamefield g9,
              gamefield g8,
              gamefield g7,
              gamefield g6,
              gamefield g5,
              gamefield g4,
              gamefield g3,
              gamefield g2,
              gamefield g1
         where g1.mask + g2.mask + g3.mask + g4.mask + g5.mask + g6.mask + g7.mask + g8.mask + g9.mask = 511
     )
select count(*)
from games;

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