diff --git a/window.cpp b/window.cpp
index 516e8bb44bd2e465c922b7201f1bf670c48bea5f..4c934172cd6cf1a50cd6680979d5b12503fad567 100644
--- a/window.cpp
+++ b/window.cpp
@@ -80,7 +80,7 @@ Window::Window(QWidget *parent)
 
 void Window::solveButtonClicked()
 {
-    std::list<History *> hist;
+    std::list<History> hist;
     bool backtracking = false;
     srand(time(NULL)); // random seed
     while (1)
@@ -89,20 +89,20 @@ void Window::solveButtonClicked()
         delay(m_delay);
         if (backtracking)
         {
-            hist.back()->cell->un();
-            if (hist.back()->index.size() == 0)
+            hist.back().cell->un();
+            if (hist.back().index.size() == 0)
             {
                     hist.pop_back();
                     continue;
                 }
             backtracking = false;
-            int choiceNr = rand() % hist.back()->index.size(); // choose a random number;
+            int choiceNr = rand() % hist.back().index.size(); // choose a random number;
             repaint();                                         // draw cells again
             delay(m_delay);
-            hist.back()->cell->collapse(hist.back()->index[choiceNr]); // collapse cell with chosen number;
+            hist.back().cell->collapse(hist.back().index[choiceNr]); // collapse cell with chosen number;
             std::vector<int>::iterator it;
-            it = hist.back()->index.begin() + choiceNr;
-            hist.back()->index.erase(it);
+            it = hist.back().index.begin() + choiceNr;
+            hist.back().index.erase(it);
         }
         else
         {
@@ -140,7 +140,7 @@ void Window::solveButtonClicked()
 
             int choiceCell = rand() % b.size();                  // choose a random cell
             int choiceNr = rand() % b[choiceCell]->index.size(); // choose a random number;
-            hist.push_back(new History(b[choiceCell], b[choiceCell]->index, choiceNr));
+            hist.push_back(History(b[choiceCell], b[choiceCell]->index, choiceNr));
             b[choiceCell]->collapse(b[choiceCell]->index[choiceNr]); // collapse that random cell with chosen number;
         }
     }