commit a0a6eca1ee2041d1264ca37e0e236208c8cb3aa2 · treybastian.com/advent-of-code

+64
2024/day_06.f90
···

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       program day_06

     

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          implicit none

     

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          character(len=130) :: line, lines(130)

     

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          integer:: io, x,y, xd,yd, i, ct

     

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          open(newunit=io, file='./day_06_input.txt', status='old', action='read')

     

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          read(io, '(a)') lines

     

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          ct = 0

     

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          ! find starting position

     

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          do i = 1, size(lines)

     

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             if (index(lines(i), '^') > 0) then

     

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                y = i

     

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                x = index(lines(i), '^')

     

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                xd = 0

     

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                yd = -1

     

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                exit

     

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             end if

     

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          end do

     

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          ! move until we leave the bounds when we hit a valid spot mark it with an X and increase count

     

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          do

     

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             ! are we going out of bounds?

     

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             if (x+xd < 1 .or. x+xd > len(lines(y)) .or. y+yd < 1 .or. y+yd > size(lines)) then

     

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                ct = ct + 1

     

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                lines(y)(x:x) = 'X'

     

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                exit

     

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             end if

     

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             ! try to move

     

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             select case(lines(y+yd)(x+xd:x+xd))

     

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              case('.')

     

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                ! valid move

     

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                ct = ct + 1

     

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                x = x + xd

     

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                y = y + yd

     

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                lines(y)(x:x) = 'X'

     

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              case('X')

     

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                ! valid move but we've been here before

     

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                x = x + xd

     

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                y = y + yd

     

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              case('#')

     

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                ! we are blocked lets rotate 90 degrees

     

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                if(xd == 0 .and. yd == -1) then

     

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                   xd = 1

     

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                   yd = 0

     

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                else if (xd == 1 .and. yd == 0) then

     

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                   xd = 0

     

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                   yd = 1

     

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                else if (xd == 0 .and. yd == 1) then

     

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                   xd = -1

     

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                   yd = 0

     

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                else if (xd == -1 .and. yd == 0) then

     

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                   xd = 0

     

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                   yd = -1

     

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                end if

     

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              case default

     

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                exit

     

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             end select

     

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          end do

     

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          print*, lines

     

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          print*, "distinct: ", ct

     

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       end program day_06

     

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