du4.2

du4/a_train.c

@@ -31,11 +31,15 @@ void print_train(struct car* first) {
 }
 
 void cancel_train(struct car* first) {
-    if (first == NULL) return;
-    cancel_train(first->next);
+    while (first) {
+        struct car* next = first->next;
+        first->next = NULL;   // ochrana proti cyklom alebo neplatnému next
         free(first);
+        first = next;
+    }
 }
 
+
 struct car* clear_train(struct car* first, const char* name) {
 
     // Ak je zoznam prázdny