commit ca6e424946a769fa52f6950047c7e46aa6f1c781 · treybastian.com/advent-of-code

+83
2024/day_03_part_2.f90
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       program day_03_part_2

     

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          implicit none

     

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          logical :: find_a, is_dont

     

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          integer ::io, ios, a, b, state, res

     

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          character(len=1) :: c

     

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          character(len=10) :: buffer

     

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          character(len=4) :: mul_cmd = 'mul('

     

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          character(len=7) :: dont_cmd = "don't()"

     

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          character(len=4) :: do_cmd = 'do()'

     

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          res = 0

     

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          open(newunit=io, file='./day_03_input.txt', status='old', action='read', access='stream')

     

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          state = 0 ! 0 = find command, 1 = find number, 2 = calculate

     

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          find_a = .true.

     

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          is_dont = .false.

     

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          buffer = ''

     

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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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             select case(state)

     

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              case (0) ! find command

     

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                buffer = trim(buffer) // c

     

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                if(is_dont) then

     

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                   if (trim(buffer) == do_cmd) then

     

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                      state = 0

     

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                      buffer = ''

     

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                      is_dont = .false.

     

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                   else if (trim(buffer) /= do_cmd(1:len(trim(buffer)))) then

     

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                      state = 0

     

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                      buffer = ''

     

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                   end if

     

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                else

     

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                   if (trim(buffer) == dont_cmd) then

     

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                      state = 0

     

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                      buffer = ''

     

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                      is_dont = .true.

     

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                   else if(trim(buffer) == mul_cmd) then

     

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                      state = 1

     

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                      buffer = ''

     

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                   else if(trim(buffer) /= mul_cmd(1:len(trim(buffer))) .and. trim(buffer) /= dont_cmd(1:len(trim(buffer)))) then

     

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                      state = 0

     

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                      buffer = ''

     

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                   end if

     

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                end if

     

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              case (1) ! find digits

     

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                select case (iachar(c))

     

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                 case (48:57) ! 0-9

     

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                   buffer = trim(buffer) // c

     

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                 case (44) ! ,

     

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                   if (find_a .and. len(trim(buffer)) > 0) then

     

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                      read(buffer, *) a

     

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                      buffer = ''

     

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                      find_a = .false.

     

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                   else

     

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                      state = 0 ! invalid

     

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                      find_a = .true.

     

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                      buffer = ''

     

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                   end if

     

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                 case (41) ! )

     

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                   if(.not. find_a .and. len(trim(buffer)) > 0) then

     

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                      read(buffer, *) b

     

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                      state = 2

     

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                      find_a = .true.

     

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                      buffer = ''

     

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                   else

     

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                      state = 0

     

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                      find_a = .true.

     

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                      buffer = ''

     

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                   end if

     

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                 case default

     

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                   state = 0

     

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                   find_a = .true.

     

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                   buffer = ''

     

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                end select

     

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             end select

     

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             if(state == 2) then

     

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                res = res + (a * b)

     

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                state = 0

     

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                buffer = ''

     

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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_03_part_2