Create second doubly linked List List2 . 2 <= > 3 <= > 7 <= > 12
head [ 1 ] = append ( head [ 1 ] , 2 ) ; head [ 1 ] = append ( head [ 1 ] , 3 ) ; head [ 1 ] = append ( head [ 1 ] , 7 ) ; head [ 1 ] = append ( head [ 1 ] , 12 ) ;