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module day_05_utils
contains
subroutine append_to_integer_array(arr, val)
integer, allocatable, intent(inout) :: arr(:)
integer, intent(in) :: val
integer, allocatable :: temp(:)
if(.not. allocated(arr)) then
ERROR STOP 'Array not allocated'
end if
allocate(temp(size(arr) + 1))
temp(1:size(arr)) = arr
temp(size(arr) + 1) = val
call move_alloc(temp, arr)
end subroutine append_to_integer_array
end module day_05_utils
program day_05
use day_05_utils
implicit none
integer :: io, ios, idx, a, b, ct, i, j, res
integer, allocatable :: left(:), right(:), print_list(:), work(:)
character(len=100) ::line
logical :: found
open(newunit=io, file='./day_05_input.txt', status='old', action='read')
res = 0
do
read(io, '(a)', iostat=ios) line
if(ios /= 0) exit !eof
idx = index(line, '|')
if(idx > 0) then ! rules
read(line(1:idx-1), *) a
read(line(idx+1:), *) b
if(.not. allocated(left)) then
allocate(left(1))
left(1) = a
else
call append_to_integer_array(left, a)
end if
if(.not. allocated(right)) then
allocate(right(1))
right(1) = b
else
call append_to_integer_array(right, b)
end if
end if
idx = index(line, ',')
if (idx > 0 ) then ! print_list
ct = 1
do i = 1 , len_trim(line)
if(line(i:i) == ',') then
ct = ct + 1
end if
end do
allocate(print_list(ct))
read(line, *) print_list
found = .false.
do i = 1, size(print_list)
if(i+1 < size(print_list)) then ! if we can check forward
do j = 1, size(right) ! find value in right and save left to work
if (print_list(i) == right(j)) then
if(.not. allocated(work)) then
allocate(work(1))
work(1) = left(j)
else
call append_to_integer_array(work, left(j))
end if
end if
end do
do j = 1, size(work)
if(any(print_list(i+1:size(print_list)) == work(j))) then
found = .true.
exit
end if
end do
deallocate(work)
end if
if(.not. found) then ! if we are still valid lets keep going
if(i-1 > 0) then ! if we can check backwards
do j = 1, size(left) ! find value in left and save left to work
if (print_list(i) == left(j)) then
if(.not. allocated(work)) then
allocate(work(1))
work(1) = right(j)
else
call append_to_integer_array(work, right(j))
end if
end if
end do
do j = 1, size(work)
if(any(print_list(1:i-1) == work(j))) then
found = .true.
exit
end if
end do
deallocate(work)
end if
else
exit
end if
end do
if (.not. found) then
res = res + print_list((size(print_list) + 1)/2)
end if
deallocate(print_list)
end if
end do
deallocate(left)
deallocate(right)
print*, "Result ", res
end program day_05
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