commit 3afa14ba25318143021da55b907dd81e2971f9a5 · treybastian.com/advent-of-code

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2024/day_07_part_2.f90
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       module day_07_part_2_utils

     

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          use iso_fortran_env, only: int64

     

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          implicit none

     

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       contains

     

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          recursive function test_values(arr, target, next_idx, current_value) result(pass)

     

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             implicit none

     

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             integer(kind=int64), intent(in) :: target, current_value, arr(:)

     

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             integer, intent(in) :: next_idx

     

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             character(len=20) :: str_1, str_2, concat_str

     

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             integer(kind=int64) :: concat_value

     

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             logical :: pass

     

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             if(next_idx > size(arr)) then

     

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                pass = current_value == target

     

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                return

     

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             end if

     

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             write(str_1, '(I0)') current_value

     

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             write(str_2, '(I0)') arr(next_idx)

     

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             concat_str = trim(str_1) // trim(str_2)

     

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             read(concat_str, '(I20)') concat_value

     

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             pass = test_values(arr, target, next_idx + 1, current_value + arr(next_idx)) .or. &

     

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                test_values(arr, target, next_idx + 1, current_value * arr(next_idx)) .or. &

     

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                test_values(arr, target, next_idx + 1, concat_value)

     

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          end function test_values

     

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          logical function is_calibrated(arr, target)

     

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             implicit none

     

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             integer(kind=int64), intent(in) :: target, arr(:)

     

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             is_calibrated = test_values(arr, target, 2, arr(1))

     

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          end function is_calibrated

     

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       end module day_07_part_2_utils

     

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       program day_07_part_2

     

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          use iso_fortran_env, only: int64

     

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          use day_07_part_2_utils

     

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          implicit none

     

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          integer(kind=int64) :: test_number, res

     

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          integer(kind=int64), allocatable:: work(:)

     

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          integer :: io, ios, idx, i, ct

     

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          character(len=200) :: line, work_line

     

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          logical :: pass

     

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          res = 0

     

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          open(newunit=io, file='./day_07_input.txt', status='old', action='read')

     

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          do

     

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             read(io, '(a)', iostat=ios) line

     

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             if (ios /= 0) exit

     

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             idx = index(line, ':')

     

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             if (idx > 0) then

     

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                read(line(1:idx-1), *) test_number

     

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                ct = 0

     

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                work_line = trim(line(idx+1:len(trim(line))))

     

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                do i = 1 , len(trim(work_line))

     

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                   if(work_line(i:i) == ' ') then

     

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                      ct = ct + 1

     

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                   end if

     

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                end do

     

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                allocate(work(ct))

     

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                read(work_line, *) work(:)

     

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             end if

     

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             pass = is_calibrated(work, test_number)

     

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             if(pass) then

     

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                res = res + test_number

     

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             end if

     

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             deallocate(work)

     

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          end do

     

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          print*, "Result: ", res

     

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       end program day_07_part_2