add

cv5/a_train.c

@@ -1,4 +1,5 @@
 #include <stdio.h>
+
 #include <stdlib.h>
 #include <string.h>
 
@@ -43,9 +44,10 @@ void cancel_train(struct car* first) {
         return;
     }
     else if(first->next != NULL){
-       cancel_train(first->next);
-       first->next = NULL;
+       struct car* help = first->next;
        free(first);
+       cancel_train(help);
+       //first->next = NULL;
     }
     else if(first->next == NULL){
         free(first);