comefrom: <awangdev>1203. Sort Items by Groups Respecting Dependencies_3.java
code: 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;
      }
masked: private Map < Integer , List < Integer >> var_0 ( List < Integer > var_1 , List < List < Integer >> var_2 ) {
    Map < Integer , List < Integer >> var_3 = new HashMap < > ( ) ;
    for ( int var_4 : var_1 ) {
      for ( int var_5 : var_2 . get ( var_4 ) ) {
        var_3 . putIfAbsent ( var_5 , new ArrayList < > ( ) ) ;
        var_3 . get ( var_5 ) . add ( var_4 ) ;
      }
    }
    return var_3 ;
  }
  