tree: fix header for potential multiple inclusions

diff --git a/tree.h b/tree.h
index 1c9f74cb440f850430b598d92c81b6f245922d33..c8f47906bbe1caf2ed866993b3dbf07e37eba63a 100644 (file)
--- a/tree.h
+++ b/tree.h
@@ -1,3 +1,6 @@
+#ifndef __TREE_H__
+#define __TREE_H__
+
 #include <set>
 #include <map>
 #include "threads.h"
@@ -29,3 +32,5 @@ private:
        std::set<tree_t> backtrack;
        static int totalNodes;
 };
+
+#endif /* __TREE_H__ */