<awangdev>1203. Sort Items by Groups Respecting Dependencies_3.java
private Map<Integer, List<Integer>> buildItemGraph(List<Integer> items, List<List<Integer>> beforeItems) {

        Map<Integer, List<Integer>> graph = new HashMap<>();
        for (int i : items) {
            for (int item : beforeItems.get(i)) {
                graph.putIfAbsent(item, new ArrayList<>());
                graph.get(item).add(i);
            }
        }
        return graph;
    }
private Map < Integer , List < Integer >> var_2 ( List < Integer > var_3 , List < List < Integer >> var_4 ) {
  Map < Integer , List < Integer >> var_7 = new HashMap < > ( ) ;
  for ( int var_8 : var_3 ) {
    for ( int var_10 : var_4 . get ( var_8 ) ) {
      var_7 . putIfAbsent ( var_10 , new ArrayList < > ( ) ) ;
      var_7 . get ( var_10 ) . add ( var_8 ) ;
    }
  }
  return var_7 ;
}
