# Problem 011

In the 20×20 grid below, four numbers along a diagonal line have been marked in red.

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

The product of these numbers is 26 × 63 × 78 × 14 = 1788696.

What is the greatest product of four adjacent numbers in any direction (up, down, left, right, or diagonally) in the 20×20 grid?

Solution:
```Function Prob011() As Long Prob011 = 0 Dim strGrid = "" strGrid &= " 08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08" strGrid &= " 49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00" strGrid &= " 81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65" strGrid &= " 52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91" strGrid &= " 22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80" strGrid &= " 24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50" strGrid &= " 32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70" strGrid &= " 67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21" strGrid &= " 24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72" strGrid &= " 21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95" strGrid &= " 78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92" strGrid &= " 16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57" strGrid &= " 86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58" strGrid &= " 19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40" strGrid &= " 04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66" strGrid &= " 88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69" strGrid &= " 04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36" strGrid &= " 20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16" strGrid &= " 20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54" strGrid &= " 01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48"```

``` Dim CharPerLine As Integer = 60 Dim Offset As Integer = 3 'Across For f As Integer = 0 To 19 Dim Val1 As Integer = 0 Dim Val2 As Integer = 0 Dim Val3 As Integer = 0 Dim Val4 As Integer = 0 Dim StartPos As Integer = (f * CharPerLine) Dim GroupCount As Integer = 1 While GroupCount < = 17 Val1 = CInt(strGrid.Substring(StartPos, Offset).Trim) Val2 = CInt(strGrid.Substring(StartPos + (Offset), Offset).Trim) Val3 = CInt(strGrid.Substring(StartPos + (Offset * 2), Offset).Trim) Val4 = CInt(strGrid.Substring(StartPos + (Offset * 3), Offset).Trim) If Val1 * Val2 * Val3 * Val4 > Prob011 Then Prob011 = Val1 * Val2 * Val3 * Val4 StartPos += Offset GroupCount += 1 End While Next 'Down For f As Integer = 0 To 16 Dim Val1 As Integer = 0 Dim Val2 As Integer = 0 Dim Val3 As Integer = 0 Dim Val4 As Integer = 0 Dim StartPos As Integer = (f * CharPerLine) Dim GroupCount As Integer = 1 While GroupCount < = 20 Val1 = CInt(strGrid.Substring(StartPos, Offset).Trim) Val2 = CInt(strGrid.Substring(StartPos + CharPerLine, Offset).Trim) Val3 = CInt(strGrid.Substring(StartPos + (CharPerLine * 2), Offset).Trim) Val4 = CInt(strGrid.Substring(StartPos + (CharPerLine * 3), Offset).Trim) If Val1 * Val2 * Val3 * Val4 > Prob011 Then Prob011 = Val1 * Val2 * Val3 * Val4 StartPos += Offset GroupCount += 1 End While Next 'Diag-Left For f As Integer = 0 To 16 Dim Val1 As Integer = 0 Dim Val2 As Integer = 0 Dim Val3 As Integer = 0 Dim Val4 As Integer = 0 Dim StartPos As Integer = (f * CharPerLine) Dim GroupCount As Integer = 1 While GroupCount < = 17 Val1 = CInt(strGrid.Substring(StartPos, Offset).Trim) Val2 = CInt(strGrid.Substring(StartPos + CharPerLine + Offset, Offset).Trim) Val3 = CInt(strGrid.Substring(StartPos + (CharPerLine * 2) + (Offset * 2), Offset).Trim) Val4 = CInt(strGrid.Substring(StartPos + (CharPerLine * 3) + (Offset * 3), Offset).Trim) If Val1 * Val2 * Val3 * Val4 > Prob011 Then Prob011 = Val1 * Val2 * Val3 * Val4 StartPos += Offset GroupCount += 1 End While Next ```

``` 'Diag-Right For f As Integer = 0 To 16 Dim Val1 As Integer = 0 Dim Val2 As Integer = 0 Dim Val3 As Integer = 0 Dim Val4 As Integer = 0 Dim StartPos As Integer = (Offset * 3) + (f * CharPerLine) Dim GroupCount As Integer = 1 While GroupCount < = 17 Val1 = CInt(strGrid.Substring(StartPos, Offset).Trim) Val2 = CInt(strGrid.Substring(StartPos + CharPerLine - Offset, Offset).Trim) Val3 = CInt(strGrid.Substring(StartPos + (CharPerLine * 2) - (Offset * 2), Offset).Trim) Val4 = CInt(strGrid.Substring(StartPos + (CharPerLine * 3) - (Offset * 3), Offset).Trim) If Val1 * Val2 * Val3 * Val4 > Prob011 Then Prob011 = Val1 * Val2 * Val3 * Val4 StartPos += Offset GroupCount += 1 End While Next End Function```

Summary:
I had a LOT of fun figuring out a solution to this one! I was pretty sure there was a way to use a Matrix for this, but — mainly because I can’t remember the last time I’ve actually used one — I skipped the matrix and went with a slightly less elegant way.