diff --git a/librerie/exercise1/list/list.hpp b/librerie/exercise1/list/list.hpp
index 926649b..f34c545 100644
--- a/librerie/exercise1/list/list.hpp
+++ b/librerie/exercise1/list/list.hpp
@@ -45,7 +45,7 @@ protected:
     /* ********************************************************************** */
 
     // Destructor
-    ~Node() = default;
+    virtual ~Node() = default;
 
     /* ********************************************************************** */
 
@@ -83,7 +83,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~List();
+  virtual ~List();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise1/vector/vector.hpp b/librerie/exercise1/vector/vector.hpp
index 2ae8fed..99386ec 100644
--- a/librerie/exercise1/vector/vector.hpp
+++ b/librerie/exercise1/vector/vector.hpp
@@ -40,7 +40,7 @@ public:
   Vector(Vector&&)noexcept;
 
   // Destructor
-  ~Vector();
+  virtual ~Vector();
 
   // Copy assignment
    Vector& operator=(const Vector&);
diff --git a/librerie/exercise2/list/list.hpp b/librerie/exercise2/list/list.hpp
index 926649b..f34c545 100644
--- a/librerie/exercise2/list/list.hpp
+++ b/librerie/exercise2/list/list.hpp
@@ -45,7 +45,7 @@ protected:
     /* ********************************************************************** */
 
     // Destructor
-    ~Node() = default;
+    virtual ~Node() = default;
 
     /* ********************************************************************** */
 
@@ -83,7 +83,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~List();
+  virtual ~List();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise2/queue/lst/queuelst.hpp b/librerie/exercise2/queue/lst/queuelst.hpp
index 92ea410..57bfe81 100755
--- a/librerie/exercise2/queue/lst/queuelst.hpp
+++ b/librerie/exercise2/queue/lst/queuelst.hpp
@@ -47,7 +47,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~QueueLst();
+  virtual ~QueueLst();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise2/queue/queue.hpp b/librerie/exercise2/queue/queue.hpp
index ba810d8..47ff4eb 100755
--- a/librerie/exercise2/queue/queue.hpp
+++ b/librerie/exercise2/queue/queue.hpp
@@ -22,7 +22,7 @@ protected:
 public:
 
   // Destructor
-  ~Queue() = default;
+  virtual ~Queue() = default;
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise2/vector/vector.hpp b/librerie/exercise2/vector/vector.hpp
index 2ae8fed..99386ec 100644
--- a/librerie/exercise2/vector/vector.hpp
+++ b/librerie/exercise2/vector/vector.hpp
@@ -40,7 +40,7 @@ public:
   Vector(Vector&&)noexcept;
 
   // Destructor
-  ~Vector();
+  virtual ~Vector();
 
   // Copy assignment
    Vector& operator=(const Vector&);
diff --git a/librerie/exercise3/list/list.cpp b/librerie/exercise3/list/list.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise3/list/list.hpp b/librerie/exercise3/list/list.hpp
old mode 100755
new mode 100644
index 926649b..f34c545
--- a/librerie/exercise3/list/list.hpp
+++ b/librerie/exercise3/list/list.hpp
@@ -45,7 +45,7 @@ protected:
     /* ********************************************************************** */
 
     // Destructor
-    ~Node() = default;
+    virtual ~Node() = default;
 
     /* ********************************************************************** */
 
@@ -83,7 +83,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~List();
+  virtual ~List();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise3/queue/lst/queuelst.hpp b/librerie/exercise3/queue/lst/queuelst.hpp
index 92ea410..57bfe81 100755
--- a/librerie/exercise3/queue/lst/queuelst.hpp
+++ b/librerie/exercise3/queue/lst/queuelst.hpp
@@ -47,7 +47,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~QueueLst();
+  virtual ~QueueLst();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise3/queue/queue.hpp b/librerie/exercise3/queue/queue.hpp
index ba810d8..47ff4eb 100755
--- a/librerie/exercise3/queue/queue.hpp
+++ b/librerie/exercise3/queue/queue.hpp
@@ -22,7 +22,7 @@ protected:
 public:
 
   // Destructor
-  ~Queue() = default;
+  virtual ~Queue() = default;
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise3/vector/vector.cpp b/librerie/exercise3/vector/vector.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise3/vector/vector.hpp b/librerie/exercise3/vector/vector.hpp
old mode 100755
new mode 100644
index 2ae8fed..99386ec
--- a/librerie/exercise3/vector/vector.hpp
+++ b/librerie/exercise3/vector/vector.hpp
@@ -40,7 +40,7 @@ public:
   Vector(Vector&&)noexcept;
 
   // Destructor
-  ~Vector();
+  virtual ~Vector();
 
   // Copy assignment
    Vector& operator=(const Vector&);
diff --git a/librerie/exercise4/binarytree/lnk/binarytreelnk.hpp b/librerie/exercise4/binarytree/lnk/binarytreelnk.hpp
index 85c852e..09d5aa2 100755
--- a/librerie/exercise4/binarytree/lnk/binarytreelnk.hpp
+++ b/librerie/exercise4/binarytree/lnk/binarytreelnk.hpp
@@ -15,10 +15,11 @@ protected:
   protected:
 
     using BinaryTree<Data>::Node::data;
+
+  public:
     struct NodeLnk* left = nullptr;
     struct NodeLnk* right = nullptr;
 
-  public:
     struct NodeLnk& operator=(const NodeLnk&); // Copy assignment of abstract types should not be possible.
     struct NodeLnk& operator=(NodeLnk&&) noexcept; // Move assignment of abstract types should not be possible.
     bool IsLeaf() const noexcept override; // (concrete function should not throw exceptions)
diff --git a/librerie/exercise4/list/list.cpp b/librerie/exercise4/list/list.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/list/list.hpp b/librerie/exercise4/list/list.hpp
old mode 100755
new mode 100644
index 926649b..f34c545
--- a/librerie/exercise4/list/list.hpp
+++ b/librerie/exercise4/list/list.hpp
@@ -45,7 +45,7 @@ protected:
     /* ********************************************************************** */
 
     // Destructor
-    ~Node() = default;
+    virtual ~Node() = default;
 
     /* ********************************************************************** */
 
@@ -83,7 +83,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~List();
+  virtual ~List();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise4/queue/lst/queuelst.hpp b/librerie/exercise4/queue/lst/queuelst.hpp
index 92ea410..57bfe81 100755
--- a/librerie/exercise4/queue/lst/queuelst.hpp
+++ b/librerie/exercise4/queue/lst/queuelst.hpp
@@ -47,7 +47,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~QueueLst();
+  virtual ~QueueLst();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise4/queue/queue.hpp b/librerie/exercise4/queue/queue.hpp
index ba810d8..47ff4eb 100755
--- a/librerie/exercise4/queue/queue.hpp
+++ b/librerie/exercise4/queue/queue.hpp
@@ -22,7 +22,7 @@ protected:
 public:
 
   // Destructor
-  ~Queue() = default;
+  virtual ~Queue() = default;
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise4/vector/vector.cpp b/librerie/exercise4/vector/vector.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/vector/vector.hpp b/librerie/exercise4/vector/vector.hpp
old mode 100755
new mode 100644
index 2ae8fed..99386ec
--- a/librerie/exercise4/vector/vector.hpp
+++ b/librerie/exercise4/vector/vector.hpp
@@ -40,7 +40,7 @@ public:
   Vector(Vector&&)noexcept;
 
   // Destructor
-  ~Vector();
+  virtual ~Vector();
 
   // Copy assignment
    Vector& operator=(const Vector&);
diff --git a/librerie/exercise5/binarytree/lnk/binarytreelnk.hpp b/librerie/exercise5/binarytree/lnk/binarytreelnk.hpp
index 85c852e..09d5aa2 100755
--- a/librerie/exercise5/binarytree/lnk/binarytreelnk.hpp
+++ b/librerie/exercise5/binarytree/lnk/binarytreelnk.hpp
@@ -15,10 +15,11 @@ protected:
   protected:
 
     using BinaryTree<Data>::Node::data;
+
+  public:
     struct NodeLnk* left = nullptr;
     struct NodeLnk* right = nullptr;
 
-  public:
     struct NodeLnk& operator=(const NodeLnk&); // Copy assignment of abstract types should not be possible.
     struct NodeLnk& operator=(NodeLnk&&) noexcept; // Move assignment of abstract types should not be possible.
     bool IsLeaf() const noexcept override; // (concrete function should not throw exceptions)
diff --git a/librerie/exercise5/list/list.cpp b/librerie/exercise5/list/list.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise5/list/list.hpp b/librerie/exercise5/list/list.hpp
old mode 100755
new mode 100644
index 926649b..f34c545
--- a/librerie/exercise5/list/list.hpp
+++ b/librerie/exercise5/list/list.hpp
@@ -45,7 +45,7 @@ protected:
     /* ********************************************************************** */
 
     // Destructor
-    ~Node() = default;
+    virtual ~Node() = default;
 
     /* ********************************************************************** */
 
@@ -83,7 +83,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~List();
+  virtual ~List();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise5/queue/lst/queuelst.hpp b/librerie/exercise5/queue/lst/queuelst.hpp
index 92ea410..57bfe81 100755
--- a/librerie/exercise5/queue/lst/queuelst.hpp
+++ b/librerie/exercise5/queue/lst/queuelst.hpp
@@ -47,7 +47,7 @@ public:
   /* ************************************************************************ */
 
   // Destructor
-  ~QueueLst();
+  virtual ~QueueLst();
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise5/queue/queue.hpp b/librerie/exercise5/queue/queue.hpp
index ba810d8..47ff4eb 100755
--- a/librerie/exercise5/queue/queue.hpp
+++ b/librerie/exercise5/queue/queue.hpp
@@ -22,7 +22,7 @@ protected:
 public:
 
   // Destructor
-  ~Queue() = default;
+  virtual ~Queue() = default;
 
   /* ************************************************************************ */
 
diff --git a/librerie/exercise5/vector/vector.cpp b/librerie/exercise5/vector/vector.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise5/vector/vector.hpp b/librerie/exercise5/vector/vector.hpp
old mode 100755
new mode 100644
index 2ae8fed..99386ec
--- a/librerie/exercise5/vector/vector.hpp
+++ b/librerie/exercise5/vector/vector.hpp
@@ -40,7 +40,7 @@ public:
   Vector(Vector&&)noexcept;
 
   // Destructor
-  ~Vector();
+  virtual ~Vector();
 
   // Copy assignment
    Vector& operator=(const Vector&);