Improved / fixed solution ordering

1 files changed, 15 insertions, 10 deletions

diff --git a/src/alg.c b/src/alg.c
index 435954b..2b5b93f 100644
--- a/src/alg.c
+++ b/src/alg.c
@@ -15,7 +15,7 @@ static void        realloc_alg(Alg *alg, int n);
 
 static int         niss_type(Alg *a);
 static void        find_last_moves(Alg *a, bool inv, int *, int *, int *);
-static int         last_move_pair(Alg *a, bool inv);
+static int64_t     last_move_pair(Alg *a, bool inv);
 static int         compare_algs_firstmoves(Alg * a, Alg *b, bool inv);
 static int         compare_algs(const void * a, const void *b);
 
@@ -499,23 +499,28 @@ find_last_moves(Alg *a, bool inv, int *n, int *nlast, int *nslast)
         }
 }
 
-static int
+static int64_t
 last_move_pair(Alg *a, bool inv)
 {
-        /* The number of the move in the moves enum, or a higher number
-         * (working in base NMOVES) if the last two moves are parallel.
-         * -1 if there are no moves on the specified side of the alg.
-         */
+        /* Order: _ F*, _ B*, F* B*, ... U* D* */
 
-        int n, nlast, nslast;
+        static int bit[] = {
+                [F] = 16, [B] = 16,
+                [R] = 18, [L] = 18,
+                [U] = 20, [D] = 20 
+        };
+        int n, nlast, nslast, last, slast;
 
         find_last_moves(a, inv, &n, &nlast, &nslast);
 
         if (n == 0)
                 return -1;
-        if (nlast == 0 || !commute(a->move[nlast], a->move[nslast]))
-                return a->move[nlast];
-        return a->move[nlast] * NMOVES + a->move[nslast];
+
+        last = a->move[nlast];
+        slast = (nslast != -1 && commute(a->move[nlast], a->move[nslast])) ?
+            a->move[nslast] : 0;
+
+        return (slast * NMOVES + last) + (1LL << bit[base_move(last)]);
 }
 
 static int