variable namespace, function declaration fixes

include/utils.hpp

@@ -40,9 +40,11 @@ private:
   std::unordered_map<T, IdType> value_to_id_;
 };
 
-class Union { // TODO: recall right algorithm name
+class GroupsManager { // TODO: recall right algorithm name
 public:
-  Union(size_t n) {
+  GroupsManager() = default;
+
+  explicit GroupsManager(size_t n) {
     edges_.resize(n);
     ranks_.resize(n);
 
@@ -52,26 +54,34 @@ public:
     }
   }
 
-  void Connect(size_t u, size_t v) { // TODO: recall choice algorithm
-    u = GetRoot(u);
-    v = GetRoot(v);
+  void Unite(size_t u, size_t v) { // TODO: recall choice algorithm
+    u = GetGroupRoot(u);
+    v = GetGroupRoot(v);
     if (ranks_[v] >= ranks_[u]) {
       edges_[u] = v;
       ranks_[v] = std::max(ranks_[u] + 1, ranks_[v]);
     } else {
       edges_[v] = u;
+      // always ranks_[u] > ranks_[v]
     }
   }
 
-  bool IsConnected(size_t u, size_t v) {
-    return GetRoot(u) == GetRoot(v);
+  bool IsInOneGroup(size_t u, size_t v) {
+    return GetGroupRoot(u) == GetGroupRoot(v);
   }
 
-  size_t GetRoot(size_t v) {
+  size_t AddElement() {
+    size_t id = edges_.size();
+    edges_.push_back(id);
+    ranks_.push_back(1);
+    return id;
+  }
+
+  size_t GetGroupRoot(size_t v) {
     if (edges_[v] == v) {
       return v;
     }
-    return edges_[v] = GetRoot(edges_[v]);
+    return edges_[v] = GetGroupRoot(edges_[v]);
   }
 private:
   std::vector<size_t> edges_;