From a0efdb9cce9e31141c71f8bf0786fc12d33591fd Mon Sep 17 00:00:00 2001
From: Petra <petra@petras.space>
Date: Sat, 16 Dec 2023 14:44:41 +1300
Subject: [PATCH] Actual 2023 day 12 solution

More aggressively memoised
---
 2023/src/day12.f90 | 83 +++++++++++++++-------------------------------
 1 file changed, 27 insertions(+), 56 deletions(-)

diff --git a/2023/src/day12.f90 b/2023/src/day12.f90
index d5c4636..25d77d8 100644
--- a/2023/src/day12.f90
+++ b/2023/src/day12.f90
@@ -7,6 +7,7 @@ program day12
     character(max_chars) :: fline
     character(max_chars) :: springs, spt
     integer :: cache(1:20, 1:300)
+    integer(kind=b_kind) :: cache2(0:100, 0:1000, 1:1000)
     integer :: tn_spr, n_springs
     integer :: n_arguments
     integer :: n_repeats
@@ -31,7 +32,7 @@ program day12
         stop
     end if
     open(10, file=fname)
-    total_valid = 0
+    total_valid = 0_b_kind
     do i=1,max_rows
         read(10, "(a)", iostat=istat) fline
         strlen = len_trim(fline)
@@ -76,8 +77,12 @@ program day12
         print *, "Number of wildcards: ", num_wc
         print *, "Wildcard Combinations: ", 2**num_wc
         cache = -1
+        cache2 = -1_b_kind
         val = nvalid(springs, n_springs, specifiers, n_specifiers)
         print *, "Valid: ", val
+        if (val .lt. 1) then
+            stop
+        end if
         print *
         total_valid = total_valid + val
         deallocate(tspec)
@@ -93,7 +98,7 @@ program day12
             character(*), intent(in) :: springs
             integer, intent(in) :: specs(:)
             integer, intent(in) :: n_spr, n_specs
-            integer :: nv
+            integer(kind=b_kind) :: nv
             integer :: ex_dist, i, cur
             cur = 0
             do i=1, n_specs
@@ -102,35 +107,45 @@ program day12
             ex_dist = n_spr - cur + 1
             print *, "Budget: ", ex_dist
             print *, "Cnk: ", n_specs + ex_dist, ex_dist
-            nv = n_specval(springs, n_spr, specs, n_specs, 0, ex_dist, 1)
+            nv = mem_n_specval(springs, n_spr, specs, n_specs, 0, ex_dist, 1)
         end function nvalid
 
+        recursive function mem_n_specval(springs, n_spr, specs, n_specs, i_gap, budget, cur) result(nsv)
+            implicit none
+            integer, intent(in) :: n_spr, n_specs, i_gap, budget, cur
+            integer, intent(in) :: specs(:)
+            character(*), intent(in) :: springs
+            integer(kind=b_kind) :: nsv
+            nsv = cache2(i_gap, budget, cur)
+            if (nsv .eq. -1_b_kind) then
+                nsv = n_specval(springs, n_spr, specs, n_specs, i_gap, budget, cur)
+                cache2(i_gap, budget, cur) = nsv
+            end if
+        end function mem_n_specval
+
         recursive function n_specval(springs, n_spr, specs, n_specs, i_gap, budget, cur) result(nsv)
             implicit none
             integer, intent(in) :: n_spr, n_specs, i_gap, budget, cur
             integer, intent(in) :: specs(:)
             character(*), intent(in) :: springs
-            integer :: nsv
+            integer(kind=b_kind) :: nsv
             integer :: b_used, cur2, curnew, brem
             logical :: bad
             if (i_gap .eq. n_specs) then
                 ! Working on the last gap; all good so far
                 if (budget .eq. 0) then
                     ! Nothing to consider
-                    nsv = 1
+                    nsv = 1_b_kind
                 else if (scan(springs((n_spr - budget + 1):n_spr), '#') .ne. 0) then
-                    nsv = 0
+                    nsv = 0_b_kind
                 else
-                    nsv = 1
+                    nsv = 1_b_kind
                 end if
                 return
             end if
-            nsv = 0
+            nsv = 0_b_kind
             do b_used=0,budget
                 cur2 = cur + b_used
-                if (i_gap .lt. 7) then
-                    print *, i_gap, b_used, cur2, repeat('*', i_gap + 1)
-                end if
                 curnew = cur2 + specs(i_gap + 1) + 1
                 bad = .false.
                 if (.not. mem_specval(cur2, specs(i_gap + 1), springs, n_spr)) then
@@ -145,39 +160,11 @@ program day12
                 end if
                 if (.not. bad) then
                     brem = budget - b_used
-                    nsv = nsv + n_specval(springs, n_spr, specs, n_specs, i_gap + 1, brem, curnew)
+                    nsv = nsv + mem_n_specval(springs, n_spr, specs, n_specs, i_gap + 1, brem, curnew)
                 end if
             end do
         end function n_specval
 
-        subroutine pr_specs(n_spr, n_specs, specs, s_starts)
-            implicit none
-            integer, intent(in) :: n_spr, n_specs, specs(:), s_starts(:)
-            character(len=max_chars) :: pstr
-            integer :: i
-            pstr = ' '
-            pstr(1:n_spr) = repeat('.', n_spr)
-            do i=1,n_specs
-                pstr(s_starts(i):(s_starts(i) + specs(i) - 1)) = repeat('#', specs(i))
-            end do
-            print *, trim(pstr)
-        end subroutine pr_specs
-
-        function spec_test(specs, spec_starts, n_specs, springs, n_spr)
-            implicit none
-            integer, intent(in) :: specs(:), spec_starts(:), n_specs, n_spr
-            character(*), intent(in) :: springs
-            logical :: spec_test
-            integer :: i
-            spec_test = .true.
-            do i=1,n_specs
-                if (.not. specval(spec_starts(i), specs(i), springs, n_spr)) then
-                    spec_test = .false.
-                    return
-                end if
-            end do
-        end function spec_test
-
         function mem_specval(spec_start, spec_len, springs, n_spr)
             implicit none
             integer, intent(in) :: spec_start, spec_len, n_spr
@@ -242,21 +229,5 @@ program day12
             end do
         end function numstr
 
-        function Cnk(n, k)
-            implicit none
-            integer, intent(in) :: n, k
-            integer :: Cnk
-            integer :: i
-            integer :: num, den
-            num = 1
-            do i = 0, k-1
-                num = num * (n-i)
-            end do
-            den = 1
-            do i = 1, k
-                den = den * i
-            end do
-            Cnk = num/den
-        end function Cnk
 end program day12