diff --git a/modules/07_stl_containers/src/associative_containers.cpp b/modules/07_stl_containers/src/associative_containers.cpp
index 90dfcef..3651d64 100644
--- a/modules/07_stl_containers/src/associative_containers.cpp
+++ b/modules/07_stl_containers/src/associative_containers.cpp
@@ -4,18 +4,25 @@ namespace stl_containers {
 
 auto word_frequencies(const std::vector<std::string>& words)
     -> std::map<std::string, int> {
-    (void)words;
-    return {};
+    auto m = std::map<std::string, int>();
+    for (const auto& word : words) {
+        ++m[word];
+    }
+    return m;
 }
 
 auto unique_sorted(const std::vector<int>& data) -> std::set<int> {
-    (void)data;
-    return {};
+    auto s = std::set<int>();
+    for (const auto& value : data) {
+        s.insert(value);
+    }
+    return s;
 }
 
 auto invert_map(const std::map<int, std::string>& input) -> std::map<std::string, int> {
-    (void)input;
-    return {};
+    auto m = std::map<std::string, int>();
+    for (const auto&[k, v] : input) m[v] = k;
+    return m;
 }
 
 }  // namespace stl_containers