この問題は特に難しいところはないですね。各マスに対して、右・下・左下・右下に4つ進んだマスが範囲内なら積を排出します。
val s = "08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08," + "49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00," + "81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65," + "52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91," + "22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80," + "24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50," + "32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70," + "67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21," + "24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72," + "21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95," + "78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92," + "16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57," + "86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58," + "19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40," + "04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66," + "88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69," + "04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36," + "20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16," + "20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54," + "01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48," def isInRange(x :Int, y :Int, dx :Int, dy :Int) = 0 <= x + dx * (N - 1) && x + dx * (N - 1) < W && 0 <= y + dy * (N - 1) && y + dy * (N - 1) < H val N = 4 val a = s.split(',').map(_.split(' ').map(_.toInt)) val H = a.size val W = a(0).size val ds = List((1, 0), (0, 1), (-1, 1), (1, 1)) val b = for(y <- 0 to (H - 1); x <- 0 to (W - 1); (dx, dy) <- ds if isInRange(x, y, dx, dy)) yield (0 to (N - 1)).map(k => a(y+dy*k)(x+dx*k)). reduceLeft(_ * _) println (b.max)
