commit 885bc8d79ba5458e154c77783776db7d999ae8cc · treybastian.com/advent-of-code

+142
2024/day_09.f90
···

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       module day_09_utils

     

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          implicit none

     

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       contains

     

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          subroutine swap_to_first_positive_integer_from_end(arr, idx)

     

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             implicit none

     

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             integer, allocatable, intent(inout) :: arr(:)

     

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             integer, intent(in) :: idx

     

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             integer, allocatable :: temp(:)

     

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             integer :: i, res

     

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             do i = 0, size(arr) - 1

     

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                if(arr(size(arr) - i) > -1) then

     

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                   arr(idx) = arr(size(arr) - i)

     

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                   allocate(temp(size(arr) - (i +1)))

     

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                   temp = arr(1:size(arr) - (i+1))

     

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                   call move_alloc(temp, arr)

     

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                   return

     

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                end if

     

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             end do

     

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          end subroutine swap_to_first_positive_integer_from_end

     

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          subroutine append_to_integer_array_times(arr, val, times)

     

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             implicit none

     

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             integer, allocatable, intent(inout) :: arr(:)

     

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             integer, intent(in) :: val, times

     

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             integer, allocatable :: temp(:)

     

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             if(.not. allocated(arr)) then

     

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                ERROR STOP 'Array not allocated'

     

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             end if

     

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             allocate(temp(size(arr) + times))

     

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             temp(1:size(arr)) = arr

     

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             temp(size(arr) + 1:size(temp)) = val

     

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             call move_alloc(temp, arr)

     

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          end subroutine append_to_integer_array_times

     

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       end module day_09_utils

     

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       program day_09

     

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          use iso_fortran_env, only: int64

     

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          use day_09_utils

     

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          implicit none

     

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          integer :: io, ios, i, j, block_n, ct, block_start, block_end, space_start, space_end

     

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          integer(kind=int64) :: res

     

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          character(len=1) :: c

     

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          integer, allocatable :: system(:), work(:)

     

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          logical :: is_space, space_block_start

     

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          open(newunit=io, file='./day_09_input.txt', status='old', action='read', access='stream')

     

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          is_space = .false.

     

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          block_n = 0

     

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          do

     

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             read(io, iostat=ios) c

     

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             if (ios /= 0) exit

     

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             read(c, *, iostat=ios) i

     

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             if(ios /= 0) exit

     

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             if (i == 0) then

     

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                is_space = .false.

     

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                cycle

     

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             end if

     

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             if (.not. allocated(system)) then

     

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                allocate(system(i))

     

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                system(1:i) = block_n

     

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                is_space = .true.

     

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                block_n = block_n + 1

     

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             else

     

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                if (is_space) then

     

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                   call append_to_integer_array_times(system, -1, i)

     

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                   is_space = .false.

     

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                else

     

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                   call append_to_integer_array_times(system, block_n, i)

     

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                   block_n = block_n + 1

     

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                   is_space = .true.

     

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                end if

     

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             end if

     

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          end do

     

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          allocate(work(size(system)))

     

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          work = system

     

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          ct = count(work > -1)

     

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          outer: do

     

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             do i = 1, size(work)

     

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                if (i == ct) exit outer ! we are done

     

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                if(work(i) < 0) then

     

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                   call swap_to_first_positive_integer_from_end(work, i)

     

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                   exit

     

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                end if

     

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             end do

     

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          end do outer

     

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          res = 0

     

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          do i = 1, size(work)

     

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             if(work(i) > -1) then

     

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                res = res + ((i-1) * work(i))

     

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             else

     

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             end if

     

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          end do

     

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          print *, res

     

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          ! start_part_2

     

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          res = 0

     

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          deallocate(work)

     

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          allocate(work(size(system)))

     

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          work = system

     

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          block_n = -1

     

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          block_start = -1

     

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          block_end = -1

     

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          do i = 0, size(work) -1

     

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             if(block_n == -1 .and. work(size(work) - i) > -1) then

     

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                ! we are starting a block

     

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                block_end = size(work) - i

     

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                block_n = work(size(work) - i)

     

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             else if (block_n /= -1 .and. block_n /= work(size(work)-i)) then

     

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                ! we are ending the block

     

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                block_start = size(work) - i

     

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                ! lets try to move the block

     

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                space_block_start = .true.

     

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                do j = 1, size(work)

     

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                   if (j >= block_start) exit

     

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                   if(space_block_start .and. work(j) == -1) then

     

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                      space_start = j

     

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                      space_block_start = .false.

     

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                   else if (.not. space_block_start .and. work(j) /= -1) then

     

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                      space_end = j

     

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                      space_block_start = .true.

     

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                      if(space_end - space_start >= block_end - block_start) then

     

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                         work(space_start:(space_start + (block_end - (block_start +1) ))) = work((block_start +1):block_end)

     

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                         work(block_start+1:block_end) = -1

     

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                         block_n = -1

     

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                         block_start = -1

     

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                         block_end = -1

     

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                         exit

     

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                      end if

     

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                   end if

     

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                end do

     

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                block_n = work(size(work) - i)

     

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                block_end = size(work) - i

     

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                block_start = -1

     

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             end if

     

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          end do

     

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          do i = 1, size(work)

     

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             if(work(i) > -1) then

     

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                res = res + ((i-1) * work(i))

     

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             end if

     

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          end do

     

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          print *, res

     

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       end program day_09

     

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