Given Input
ArrayList < ArrayList < Integer > > arr = new ArrayList < > ( ) ; arr . add ( new ArrayList < > ( Arrays . asList ( 1 , 2 , 2 , 1 ) ) ) ; arr . add ( new ArrayList < > ( Arrays . asList ( 3 , 1 , 2 ) ) ) ; arr . add ( new ArrayList < > ( Arrays . asList ( 1 , 3 , 2 ) ) ) ; arr . add ( new ArrayList < > ( Arrays . asList ( 2 , 4 ) ) ) ; arr . add ( new ArrayList < > ( Arrays . asList ( 3 , 1 , 2 ) ) ) ; arr . add ( new ArrayList < > ( Arrays . asList ( 1 , 3 , 1 , 1 ) ) ) ;