feat: add bucket finder

lib_vector_search/include/bucket_finder.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include "finder.h"
+#include "word_list.h"
+
+#include <map>
+
+class Bucket {
+private:
+  std::map<const char, WordRefList> groups_;
+
+public:
+  Bucket() = default;
+
+  void insert(const WordList &word_list, size_t first_index, size_t last_index);
+
+  std::forward_list<const std::string *>
+  find_prefix(std::string_view search_term) const;
+};
+
+class BucketFinder : public Finder {
+private:
+  std::vector<Bucket> buckets_;
+
+public:
+  BucketFinder(const WordList &word_list);
+
+  std::forward_list<const std::string *>
+  find_prefix(std::string_view search_term) const override;
+};

lib_vector_search/include/word_list.h

@@ -22,6 +22,7 @@ public:
 
 class WordRefList : public std::vector<const std::string *> {
 public:
+  WordRefList() = default;
   WordRefList(const WordList &source);
 
   static void find_prefix_in_range(