正方形内から3つ進んだところが正方形内なら積を取ることができます。
とにかく,（カンマ）の優先順位が高いのが分かっていても感覚と合わないからすぐに間違えます。
function fold($f, $init) {
begin { $x = $init }
process { $x = & $f $x $_ }
end { $x }
}
function product($a) {
return $a | fold { $args[0] * $args[1] } 1
}
$s = "08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08\n" +
"49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00\n" +
"81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65\n" +
"52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91\n" +
"22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80\n" +
"24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50\n" +
"32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70\n" +
"67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21\n" +
"24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72\n" +
"21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95\n" +
"78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92\n" +
"16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57\n" +
"86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58\n" +
"19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40\n" +
"04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66\n" +
"88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69\n" +
"04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36\n" +
"20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16\n" +
"20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54\n" +
"01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48"
function max_product($a) {
$n = $a.length
(0..($n-4) | foreach { product $a[$_..($_+3)] } | measure -max).Maximum
}
function is_in_square($x, $y) {
0 -le $x -and $x -lt $N -and 0 -le $y -and $y -lt $N
}
function gen_seqs($A) {
foreach($d in @(@(1, 0), @(0, 1), @(1, 1), @(1, -1))) {
foreach($x in 0..($N - 1)) {
foreach($y in 0..($N - 1)) {
$x1 = $x + $d[0] * ($L - 1)
$y1 = $y + $d[1] * ($L - 1)
if(is_in_square $x1 $y1) {
,(0..($L - 1) | foreach {
$A[$y + $d[1] * $_][$x + $d[0] * $_] })
}
}
}
}
}
$A = $s -split "\\n" | foreach { ,($_ -split " " | foreach { [int]$_ }) }
$N = $A.length
$L = 4
gen_seqs $A | foreach { product $_ } | measure -max
