comefrom: <awangdev>743. Network Delay Time_2.java
code: private Map<Integer, List<int[]>> buildGraph(int[][] times) {
  
          Map<Integer, List<int[]>> graph = new HashMap<>();
          for (int[] record : times) {
              graph.putIfAbsent(record[0], new ArrayList<>());
              graph.get(record[0]).add(record);
          }
          return graph;
      }
masked: private Map < Integer , List < int [ ] >> var_2 ( int [ ] [ ] var_3 ) {
    Map < Integer , List < int [ ] >> var_6 = new HashMap < > ( ) ;
    for ( int [ ] var_7 : var_3 ) {
      var_6 . putIfAbsent ( var_7 [ 0 ] , new ArrayList < > ( ) ) ;
      var_6 . get ( var_7 [ 0 ] ) . add ( var_7 ) ;
    }
    return var_6 ;
  }
  