day 6 part 1

1 files changed, 64 insertions, 0 deletions

diff --git a/2024/day_06.f90 b/2024/day_06.f90
new file mode 100644
index 0000000..46ba2cf
--- /dev/null
+++ b/2024/day_06.f90
@@ -0,0 +1,64 @@
+program day_06
+   implicit none
+   character(len=130) :: line, lines(130)
+   integer:: io, x,y, xd,yd, i, ct
+
+   open(newunit=io, file='./day_06_input.txt', status='old', action='read')
+   read(io, '(a)') lines
+
+   ct = 0
+   ! find starting position
+   do i = 1, size(lines)
+      if (index(lines(i), '^') > 0) then
+         y = i
+         x = index(lines(i), '^')
+         xd = 0
+         yd = -1
+         exit
+      end if
+   end do
+
+   ! move until we leave the bounds when we hit a valid spot mark it with an X and increase count
+   do
+      ! are we going out of bounds?
+      if (x+xd < 1 .or. x+xd > len(lines(y)) .or. y+yd < 1 .or. y+yd > size(lines)) then
+         ct = ct + 1
+         lines(y)(x:x) = 'X'
+         exit
+      end if
+
+      ! try to move
+      select case(lines(y+yd)(x+xd:x+xd))
+       case('.')
+         ! valid move
+         ct = ct + 1
+         x = x + xd
+         y = y + yd
+         lines(y)(x:x) = 'X'
+       case('X')
+         ! valid move but we've been here before
+         x = x + xd
+         y = y + yd
+       case('#')
+         ! we are blocked lets rotate 90 degrees
+         if(xd == 0 .and. yd == -1) then
+            xd = 1
+            yd = 0
+         else if (xd == 1 .and. yd == 0) then
+            xd = 0
+            yd = 1
+         else if (xd == 0 .and. yd == 1) then
+            xd = -1
+            yd = 0
+         else if (xd == -1 .and. yd == 0) then
+            xd = 0
+            yd = -1
+         end if
+       case default
+         exit
+      end select
+   end do
+   print*, lines
+   print*, "distinct: ", ct
+end program day_06
+