2020/16

dlx/src/dlx.cpp

@@ -228,43 +228,42 @@ auto Dlx::RemoveRow(std::size_t i) -> void {
 }
 
 auto Dlx::Solve(
-  std::function<void(std::size_t, std::size_t, std::size_t)> try_cb,
-  std::function<void()> undo_cb,
-  std::function<void()> found_cb,
-  std::function<void(std::size_t)> stuck_cb) -> void
+  std::function<bool(std::size_t, std::size_t, std::size_t)> try_cb,
+  std::function<bool()> undo_cb,
+  std::function<bool()> found_cb,
+  std::function<bool(std::size_t)> stuck_cb) -> void
 {
-  auto const recurse = [&](auto const& self) -> void {
+  auto const recurse = [&](auto const& self) -> bool {
     auto c = root_->R;
     if (c == root_) {
-      found_cb();
-      return;
+      return found_cb();
     }
 
-    auto s = std::numeric_limits<std::size_t>::max();
+    auto s = c->s;
     for (auto const i : root_->rightwards()) {
       if (i->s < s) {
         s = (c = i)->s;
-
-        if (s == 0) {
-          stuck_cb(c->n);
-          return;
-        }
       }
     }
 
+    if (s == 0) {
+      return stuck_cb(c->n);
+    }
+
     c->CoverCol();
     for (auto const r : c->downwards()) {
-      try_cb(c->n, s, r->n);
+      if (try_cb(c->n, s, r->n)) [[unlikely]] return true;
       for (auto const j : r->rightwards()) {
         j->c->CoverCol();
       }
-      self(self);
-      undo_cb();
+      if (self(self)) [[unlikely]] return true;
+      if (undo_cb()) [[unlikely]] return true;
       for (auto const j : r->leftwards()) {
         j->c->UncoverCol();
       }
     }
     c->UncoverCol();
+    return false;
   };
   recurse(recurse);
 }