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module day_07_utils
use iso_fortran_env, only: int64
implicit none
contains
recursive function test_values(arr, target, next_idx, current_value) result(pass)
implicit none
integer(kind=int64), intent(in) :: target, current_value, arr(:)
integer, intent(in) :: next_idx
logical :: pass
if(next_idx > size(arr)) then
pass = current_value == target
return
end if
pass = test_values(arr, target, next_idx + 1, current_value + arr(next_idx)) .or. &
test_values(arr, target, next_idx + 1, current_value * arr(next_idx))
end function test_values
logical function is_calibrated(arr, target)
implicit none
integer(kind=int64), intent(in) :: target, arr(:)
is_calibrated = test_values(arr, target, 2, arr(1))
end function is_calibrated
end module day_07_utils
program day_07
use iso_fortran_env, only: int64
use day_07_utils
implicit none
integer(kind=int64) :: test_number, res
integer(kind=int64), allocatable:: work(:)
integer :: io, ios, idx, i, ct
character(len=200) :: line, work_line
logical :: pass
res = 0
open(newunit=io, file='./day_07_input.txt', status='old', action='read')
do
read(io, '(a)', iostat=ios) line
if (ios /= 0) exit
idx = index(line, ':')
if (idx > 0) then
read(line(1:idx-1), *) test_number
ct = 0
work_line = trim(line(idx+1:len(trim(line))))
do i = 1 , len(trim(work_line))
if(work_line(i:i) == ' ') then
ct = ct + 1
end if
end do
allocate(work(ct))
read(work_line, *) work(:)
end if
pass = is_calibrated(work, test_number)
if(pass) then
res = res + test_number
end if
deallocate(work)
end do
print*, "Result: ", res
end program day_07
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