Improved comments

1 files changed, 49 insertions, 10 deletions

diff --git a/cube.c b/cube.c
index 3ba3926..cd93d48 100644
--- a/cube.c
+++ b/cube.c
@@ -3688,19 +3688,51 @@ implementation of all the solving algorithms.
 
 typedef struct {
         cube_t cube;
-        int (*estimate)(cube_t);
         uint8_t depth;
         int maxsols;
         move_t *sols;
         int nsols;
         int nmoves;
         move_t moves[20];
+        int (*estimate)(cube_t);
 } dfs_arg_t;
 
-int
+static bool
+allowednextmove(dfs_arg_t arg, move_t m)
+{
+        int n;
+        move_t mbase, l1base, l2base, maxis, l1axis, l2axis;
+
+        n = arg.nmoves;
+
+        if (n == 0)
+                return true;
+
+        mbase = m / 3;
+        maxis = mbase / 2;
+        l1base = arg.moves[n-1] / 3;
+        l1axis = l1base / 2;
+
+        if (mbase == l1base || (maxis == l1axis && mbase < l1base))
+                return false;
+
+        if (n == 1)
+                return true;
+
+        l2base = arg.moves[n-2] / 3;
+        l2axis = l1base / 2;
+
+        return l1axis != l2axis || mbase != l2base;
+}
+
+static int
 solve_generic_dfs(dfs_arg_t arg)
 {
-        int bound = arg.estimate(arg.cube);
+        dfs_arg_t nextarg;
+        int bound, ret;
+        move_t m;
+
+        bound = arg.estimate(arg.cube);
 
         if (arg.nsols == arg.maxsols || bound + arg.nmoves > arg.depth)
                 return 0;
@@ -3714,36 +3746,43 @@ solve_generic_dfs(dfs_arg_t arg)
                 return 1;
         }
 
-        /* TODO: loop over moves and recur */
-        return 0;
+        memcpy(&nextarg, &arg, sizeof(dfs_arg_t));
+        nextarg.nmoves = arg.nmoves + 1;
+        for (m = 0, ret = 0; m < 18; m++) {
+                if (allowednextmove(arg, m)) {
+                        nextarg.cube = move(arg.cube, m);
+                        nextarg.moves[arg.nmoves] = m;
+                        ret += solve_generic_dfs(nextarg);
+                }
+        }
+
+        return ret;
 }
 
 int
 solve_generic(
         cube_t cube,
-        int (*estimate)(cube_t),
         uint8_t depth,
         int maxsols,
         move_t *sols
+        int (*estimate)(cube_t),
 )
 {
         dfs_arg_t arg;
 
-        if (!issolvable(cube) || depth > 20)
+        if (!issolvable(cube) || depth > 20 || estimate == NULL)
                 return -1;
 
         arg = (dfs_arg_t) {
                 .cube = cube,
-                .estimate = estimate,
                 .depth = depth,
                 .maxsols = maxsols,
                 .sols = sols,
                 .nsols = 0,
                 .nmoves = 0,
                 .moves = {0}
+                .estimate = estimate,
         };
 
         return solve_generic_dfs(arg);
-
-        return 0;
 }