2 08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
3 49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
4 81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
5 52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
6 22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
7 24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
8 32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
9 67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
10 24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
11 21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
12 78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
13 16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
14 86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
15 19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
16 04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
17 88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
18 04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
19 20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
20 20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
21 01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48 }
24 grid_line
.map
{|s
| s
.to_i
}.each_slice(20) {|s
| $grid << s
}
27 def find_largest_product
31 largest_direction
= :east
32 $grid.length
.times
do |row
|
33 $grid[0].length
.times
do |column
|
34 [:east, :south_east, :south, :south_west].each
do |direction
|
35 this_product
= find_product($grid, row
, column
, direction
, $line_length)
36 if this_product
> largest
37 largest
= this_product
39 largest_column
= column
40 largest_direction
= direction
45 return largest
, largest_row
, largest_column
, largest_direction
48 def offsets_of_direction(direction
)
69 def find_product(grid
, row
, column
, direction
, line_length
)
70 row_change
, column_change
= offsets_of_direction(direction
)
71 end_row
= row
+ row_change
* (line_length
- 1)
72 end_column
= column
+ column_change
* (line_length
- 1)
73 return 0 unless (0...grid
.length
).include? end_row
and
74 (0...grid
[0].length
).include? end_column
76 rows
= [row
] * line_length
78 rows
= row
.step(end_row
, row_change
).to_a
81 cols
= [column
] * line_length
83 cols
= column
.step(end_column
, column_change
).to_a
85 rows
.zip(cols
).reduce(1) {|product
, i
| product
*= grid
[i
[0]][i
[1]]}
89 puts find_largest_product
[0]