refactor: make day 5 part 2 code fast

list.h

@@ -52,6 +52,10 @@ static __inline void LIST_FN(remove)(LIST_NAME *alist, int index) {
 #endif //LIST_UNORDERED
 }
 
+static __inline void LIST_FN(clear)(LIST_NAME *alist) {
+    alist->length = 0;
+}
+
 static __inline void LIST_FN(free)(LIST_NAME *alist) {
     free(alist->data);
     free(alist);