My yearly advent-of-code solutions
treybastian.com
1module day_09_utils
2 implicit none
3contains
4 subroutine swap_to_first_positive_integer_from_end(arr, idx)
5 implicit none
6 integer, allocatable, intent(inout) :: arr(:)
7 integer, intent(in) :: idx
8 integer, allocatable :: temp(:)
9 integer :: i, res
10 do i = 0, size(arr) - 1
11 if(arr(size(arr) - i) > -1) then
12 arr(idx) = arr(size(arr) - i)
13 allocate(temp(size(arr) - (i +1)))
14 temp = arr(1:size(arr) - (i+1))
15 call move_alloc(temp, arr)
16 return
17 end if
18 end do
19 end subroutine swap_to_first_positive_integer_from_end
20 subroutine append_to_integer_array_times(arr, val, times)
21 implicit none
22 integer, allocatable, intent(inout) :: arr(:)
23 integer, intent(in) :: val, times
24 integer, allocatable :: temp(:)
25 if(.not. allocated(arr)) then
26 ERROR STOP 'Array not allocated'
27 end if
28 allocate(temp(size(arr) + times))
29 temp(1:size(arr)) = arr
30 temp(size(arr) + 1:size(temp)) = val
31 call move_alloc(temp, arr)
32 end subroutine append_to_integer_array_times
33end module day_09_utils
34program day_09
35 use iso_fortran_env, only: int64
36 use day_09_utils
37 implicit none
38 integer :: io, ios, i, j, block_n, ct, block_start, block_end, space_start, space_end
39 integer(kind=int64) :: res
40 character(len=1) :: c
41 integer, allocatable :: system(:), work(:), done(:)
42 logical :: is_space, space_block_start
43
44 open(newunit=io, file='./day_09_input.txt', status='old', action='read', access='stream')
45 is_space = .false.
46 block_n = 0
47 do
48 read(io, iostat=ios) c
49 if (ios /= 0) exit
50 read(c, *, iostat=ios) i
51 if(ios /= 0) exit
52 if (i == 0) then
53 is_space = .false.
54 cycle
55 end if
56 if (.not. allocated(system)) then
57 allocate(system(i))
58 system(1:i) = block_n
59 is_space = .true.
60 block_n = block_n + 1
61 else
62 if (is_space) then
63 call append_to_integer_array_times(system, -1, i)
64 is_space = .false.
65 else
66 call append_to_integer_array_times(system, block_n, i)
67 block_n = block_n + 1
68 is_space = .true.
69 end if
70 end if
71 end do
72 allocate(work(size(system)))
73 work = system
74 ct = count(work > -1)
75 outer: do
76 do i = 1, size(work)
77 if (i == ct) exit outer ! we are done
78 if(work(i) < 0) then
79 call swap_to_first_positive_integer_from_end(work, i)
80 exit
81 end if
82 end do
83 end do outer
84 res = 0
85 do i = 1, size(work)
86 if(work(i) > -1) then
87 res = res + ((i-1) * work(i))
88 else
89 end if
90 end do
91 print *, res
92 ! start_part_2
93 res = 0
94 deallocate(work)
95 allocate(work(size(system)))
96 work = system
97 block_n = -1
98 block_start = -1
99 block_end = -1
100 do i = size(work), 1, -1
101 if(block_n == -1 .and. work(i) /= -1) then
102 ! we are starting a block
103 block_end = i
104 block_n = work(i)
105 if(allocated(done) .and. count(done == block_n) > 0) then
106 block_n = -1
107 block_start = -1
108 block_end = -1
109 cycle
110 else if(.not. allocated(done)) then
111 allocate(done(1))
112 done(1) = block_n
113 else
114 call append_to_integer_array_times(done, block_n, 1)
115 end if
116 else if (block_n /= -1 .and. block_n /= work(i)) then
117 ! we are ending the block
118 block_start = i
119
120 ! lets try to move the block
121 space_block_start = .true.
122 do j = 1, size(work)
123 if (j > block_start) exit
124 if(space_block_start .and. work(j) == -1) then
125 space_start = j
126 space_block_start = .false.
127 else if (.not. space_block_start .and. work(j) /= -1) then
128 space_end = j
129 space_block_start = .true.
130 if(space_end - space_start >= block_end - block_start) then
131 work(space_start:space_start + (block_end - (block_start +1))) = block_n
132 work(block_start+1:block_end) = -1
133 exit
134 end if
135 space_end = -1
136 space_start = -1
137 end if
138 end do
139 block_n = work(i)
140 block_end = i
141 block_start = -1
142 end if
143 end do
144 do i = 1, size(work)
145 if(work(i) /= -1) then
146 res = res + ((i-1) * work(i))
147 end if
148 end do
149 print *, res
150end program day_09
151
152