user
Task

The task description is taken from Project Euler:
  
(https://projecteuler.net/problem=11)
  
  
Given the 20×20 grid below:

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
  
  
What is the greatest product of four adjacent numbers in the same direction (down, right) in the 20×20 grid?
assistant
General solution. No hard coded values. Works with any size matrix, configurable number of terms.

```
my @matrix = q:to/END/.lines».words;
  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 
END

my $terms = 4;

say "Largest product of $terms adjacent elements: " ~ max flat (^@matrix).map: {
    @matrix.rotor($terms => -$terms+1).flat»[$_].batch($terms)».reduce(&[*]), # vertical
    @matrix[$_].rotor($terms => -$terms+1)».reduce(&[*]);                     # horizontal
}

```

Output:

```
Largest product of 4 adjacent elements: 51267216
```