dlx: nicer iteration

dlx/include/dlx.hpp

@@ -7,30 +7,9 @@
 
 namespace dlx {
 
+struct Cell;
+
 class Dlx final {
-
-  struct Cell {
-    Cell *U, *D, *L, *R;
-    std::size_t n;
-    union {
-      Cell* c;
-      std::size_t s;
-    };
-
-    auto LR_self() -> void;
-    auto UD_self() -> void;
-    auto LR_delete() -> void;
-    auto UD_delete() -> void;
-    auto UD_restore() -> void;
-    auto LR_restore() -> void;
-    auto LR_insert(Cell* k) -> void;
-    auto UD_insert(Cell* k) -> void;
-    auto CoverCol() -> void;
-    auto UncoverCol() -> void;
-    auto ColAdd(std::size_t row_id) -> Cell*;
-    static Cell* ColNew();
-  };
-
   std::vector<Cell*> ctab_;
   std::vector<Cell*> rtab_;
   Cell* root_;