July Hack Night

dojo4.erl

-module(dojo4).
-import(lists,[nth/2]).
-include_lib ("eunit/include/eunit.hrl").
-compile(export_all).

rand_list(Size) ->
    lists:map(fun(X)-> random:uniform(100) end, lists:seq(1,Size)).

grid(Size) ->
    lists:map(fun(X)-> rand_list(Size) end, lists:seq(1,Size)).

fix_grid(Size)->
    lists:map(fun(X)-> lists:seq(1,Size) end, lists:seq(1,Size)).

multiply([H|T],[HH|TT])->
    [H*HH|multiply(T,TT)];
multiply([],[])->
    [].

mult_by_rows([F|REST],[FF|RREST])->
    [multiply(F,FF)|mult_by_rows(REST,RREST)];
mult_by_rows([],[])->
    [].

shift_col(Xs)->
    lists:map(fun([F|Ys]) -> Ys ++ [F] end, Xs).

shift_col_reverse(Xs)->
    lists:map(fun(F)->[lists:last(F) | lists:droplast(F)] end, Xs).

transpose([[]|_]) -> [];
transpose(M) ->
    [lists:map(fun hd/1, M) | transpose(lists:map(fun tl/1, M))].

shift_diag(Xs)->
    transpose(shift_col_reverse(transpose(shift_col_reverse(Xs)))).
shift_diag2(Xs)->
    transpose(shift_col(transpose(shift_col_reverse(Xs)))).

calc_rows(M) ->
    M1 = shift_col(M),
    M2 = shift_col(M1),
    M3 = shift_col(M2),
    lists:max(lists:flatten(lists:foldl(fun(E,A)-> mult_by_rows(A,E) end, M, [M1,M2,M3]))).
calc_col(M) ->
    calc_rows(transpose(M)).
calc_diag(M)->
    M1 = shift_diag(M),    M2 = shift_diag(M1),    M3 = shift_diag(M2),
    lists:max(lists:flatten(lists:foldl(fun(E,A)-> mult_by_rows(A,E) end, M, [M1,M2,M3]))).
calc_diag2(M)->
    M1 = shift_diag2(M),    M2 = shift_diag2(M1),    M3 = shift_diag2(M2),
    lists:max(lists:flatten(lists:foldl(fun(E,A)-> mult_by_rows(A,E) end, M, [M1,M2,M3]))).
calc(M)->
    lists:max([calc_rows(M),calc_col(M),calc_diag(M),calc_diag2(M)]).

calc_test() ->
    G = fix_grid(10),
    ?assertEqual(10000, calc(G)).