Fortran Implementation of Problem 11
View source code here on GitHub!
- integer Problem0011/p0011()
1! Project Euler Problem 11
2!
3! Problem:
4!
5! In the 20×20 grid below, four numbers along a diagonal line have been marked in red.
6!
7! 08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
8! 49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
9! 81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
10! 52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
11! 22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
12! 24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
13! 32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
14! 67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
15! 24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
16! 21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
17! 78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
18! 16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
19! 86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
20! 19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
21! 04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
22! 88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
23! 04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
24! 20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
25! 20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
26! 01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48
27!
28! The product of these numbers is 26 × 63 × 78 × 14 = 1788696.
29!
30! What is the greatest product of four adjacent numbers in the same direction (up, down, left, right, or diagonally) in
31! the 20×20 grid?
32
33module Problem0011
34 use constants
35 implicit none
36contains
37 integer(i18t) function p0011() result(answer)
38 integer(i2t), dimension(20, 20) :: grid
39 integer(i18t) :: tmp
40 integer :: i, j
41
42 ! Manually initialize the grid
43 data grid / &
44 8, 2, 22, 97, 38, 15, 0, 40, 0, 75, 4, 5, 7, 78, 52, 12, 50, 77, 91, 8, &
45 49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 4, 56, 62, 0, &
46 81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 3, 49, 13, 36, 65, &
47 52, 70, 95, 23, 4, 60, 11, 42, 69, 24, 68, 56, 1, 32, 56, 71, 37, 2, 36, 91, &
48 22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80, &
49 24, 47, 32, 60, 99, 3, 45, 2, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50, &
50 32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70, &
51 67, 26, 20, 68, 2, 62, 12, 20, 95, 63, 94, 39, 63, 8, 40, 91, 66, 49, 94, 21, &
52 24, 55, 58, 5, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72, &
53 21, 36, 23, 9, 75, 0, 76, 44, 20, 45, 35, 14, 0, 61, 33, 97, 34, 31, 33, 95, &
54 78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 3, 80, 4, 62, 16, 14, 9, 53, 56, 92, &
55 16, 39, 5, 42, 96, 35, 31, 47, 55, 58, 88, 24, 0, 17, 54, 24, 36, 29, 85, 57, &
56 86, 56, 0, 48, 35, 71, 89, 7, 5, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58, &
57 19, 80, 81, 68, 5, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 4, 89, 55, 40, &
58 4, 52, 8, 83, 97, 35, 99, 16, 7, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66, &
59 88, 36, 68, 87, 57, 62, 20, 72, 3, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69, &
60 4, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 8, 46, 29, 32, 40, 62, 76, 36, &
61 20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 4, 36, 16, &
62 20, 73, 35, 29, 78, 31, 90, 1, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 5, 54, &
63 1, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 1, 89, 19, 67, 48 /
64 answer = 0
65
66 do i = 1, 20
67 do j = 1, 17
68 ! Horizontal section
69 tmp = int(grid(i, j), kind=8) * grid(i, j + 1) * grid(i, j + 2) * grid(i, j + 3)
70 answer = max(answer, tmp)
71
72 ! Vertical section
73 tmp = int(grid(j, i), kind=8) * grid(j + 1, i) * grid(j + 2, i) * grid(j + 3, i)
74 answer = max(answer, tmp)
75 end do
76 end do
77
78 do i = 1, 17
79 do j = 1, 17
80 ! Right diagonal section
81 tmp = int(grid(i, j), kind=8) * grid(i + 1, j + 1) * grid(i + 2, j + 2) * grid(i + 3, j + 3)
82 answer = max(answer, tmp)
83
84 ! Left diagonal section
85 tmp = int(grid(i, j + 3), kind=8) * grid(i + 1, j + 2) * grid(i + 2, j + 1) * grid(i + 3, j)
86 answer = max(answer, tmp)
87 end do
88 end do
89 end function p0011
90end module Problem0011