creating undirected edges
adj [ 1 ] . push ( 2 ) ; adj [ 2 ] . push ( 1 ) ; adj [ 1 ] . push ( 3 ) ; adj [ 3 ] . push ( 1 ) ; adj [ 2 ] . push ( 4 ) ; adj [ 4 ] . push ( 2 ) ; adj [ 2 ] . push ( 5 ) ; adj [ 5 ] . push ( 2 ) ; adj [ 2 ] . push ( 6 ) ; adj [ 6 ] . push ( 2 ) ; printDiameters ( adj ) ;