day 4 part 2

1 files changed, 39 insertions, 0 deletions

diff --git a/2024/day_04_part_2.f90 b/2024/day_04_part_2.f90
new file mode 100644
index 0000000..ed363ac
--- /dev/null
+++ b/2024/day_04_part_2.f90
@@ -0,0 +1,39 @@
+program day_04
+   implicit none
+   character(len=140) ::  lines(140)
+   character(len=1) :: c
+   integer :: io, row, col, score, z
+   logical :: left_m, right_m
+
+   left_m = .false.
+   right_m = .false.
+   score = 0
+   open(newunit=io, file='./day_04_input.txt', status='old', action='read')
+   read(io, '(a)') lines
+   do row = 2, size(lines) - 1
+      do col = 2, len(lines(row)) - 1
+         if (lines(row)(col:col) == 'A') then
+            c = lines(row-1)(col-1:col-1)
+            if (c == 'S' .or. c == 'M') then
+               left_m = c == 'M'
+               c = lines(row-1)(col+1:col+1)
+               if (c == 'S' .or. c == 'M') then
+                  right_m = c == 'M'
+                  c = lines(row+1)(col-1:col-1)
+                  if (right_m .and. c == 'S' .or. (.not. right_m .and. c == 'M')) then
+                     c = lines(row+1)(col+1:col+1)
+                     if (left_m .and. c == 'S' .or. (.not. left_m .and. c =='M')) then
+                        score = score + 1
+                     end if
+                  end if
+               end if
+            end if
+         end if
+         left_m = .false.
+         right_m = .false.
+         c = ''
+      end do
+   end do
+   print*, score
+
+end program day_04