My yearly advent-of-code solutions
treybastian.com
1program day_06
2 implicit none
3 character(len=130) :: line, lines(130)
4 integer:: io, x,y, xd,yd, i, ct
5
6 open(newunit=io, file='./day_06_input.txt', status='old', action='read')
7 read(io, '(a)') lines
8
9 ct = 0
10 ! find starting position
11 do i = 1, size(lines)
12 if (index(lines(i), '^') > 0) then
13 y = i
14 x = index(lines(i), '^')
15 xd = 0
16 yd = -1
17 exit
18 end if
19 end do
20
21 ! move until we leave the bounds when we hit a valid spot mark it with an X and increase count
22 do
23 ! are we going out of bounds?
24 if (x+xd < 1 .or. x+xd > len(lines(y)) .or. y+yd < 1 .or. y+yd > size(lines)) then
25 ct = ct + 1
26 lines(y)(x:x) = 'X'
27 exit
28 end if
29
30 ! try to move
31 select case(lines(y+yd)(x+xd:x+xd))
32 case('.')
33 ! valid move
34 ct = ct + 1
35 x = x + xd
36 y = y + yd
37 lines(y)(x:x) = 'X'
38 case('X')
39 ! valid move but we've been here before
40 x = x + xd
41 y = y + yd
42 case('#')
43 ! we are blocked lets rotate 90 degrees
44 if(xd == 0 .and. yd == -1) then
45 xd = 1
46 yd = 0
47 else if (xd == 1 .and. yd == 0) then
48 xd = 0
49 yd = 1
50 else if (xd == 0 .and. yd == 1) then
51 xd = -1
52 yd = 0
53 else if (xd == -1 .and. yd == 0) then
54 xd = 0
55 yd = -1
56 end if
57 case default
58 exit
59 end select
60 end do
61 print*, lines
62 print*, "distinct: ", ct
63end program day_06
64