feat: add tree-finder

lib_vector_search/src/tree_finder.cpp

@@ -0,0 +1,53 @@
+#include "tree_finder.h"
+
+void SearchTreeNode::insert(std::string_view partial_word,
+                            const string *original_word) {
+  if (partial_word.empty()) {
+    words_.push_front(original_word);
+  } else {
+    children_[partial_word.front()].insert(
+        std::string_view(partial_word).substr(1, partial_word.length()),
+        original_word);
+  }
+}
+
+const SearchTreeNode *SearchTreeNode::find(std::string_view search_term) const {
+  if (search_term.empty()) {
+    return this;
+  }
+
+  auto child = children_.find(search_term.front());
+  if (child != children_.cend()) {
+    return child->second.find(search_term.substr(1, search_term.length()));
+  }
+
+  return nullptr;
+}
+
+std::forward_list<const std::string *> SearchTreeNode::words() const {
+  std::forward_list<const std::string *> results(words_);
+  for (const auto &child : children_) {
+    results.merge(child.second.words());
+  }
+
+  return results;
+};
+
+SearchTree::SearchTree(const std::vector<std::string> &word_list) {
+  for (const auto &word : word_list) {
+    insert(std::string_view(word), &word);
+  }
+}
+
+TreeFinder::TreeFinder(const std::vector<string> &word_list)
+    : search_tree_(word_list) {}
+
+std::forward_list<const std::string *>
+TreeFinder::find_prefix(std::string_view search_term) const {
+  const auto *result_node = search_tree_.find(search_term);
+  if (result_node == nullptr) {
+    return {};
+  }
+
+  return result_node->words();
+}