Here is a quick sketch of the solutions.
In grading, I am looking only for a few things on each question,
and an overall understanding of the important concepts.

1. (a) O( N^2 ) because of the nested loops, and the calls to get are O(1)
   (b) O( N^3 ) because of the nested loops, and each get is O(N)time
   (c) For a quadratic algorithm, when N is increased
       by a factor of 2, the running time increases
       by a factor of 4. So the time will be 40 sec.
   (d) Use an iterator to get an O( N^2 ) algorithm for all types of lists.
       OR... sort both lists and do a sequential scan of the lists
       which will be even faster.

2. (a) toArray is O(N) the other two are O(1).

   (b)
     public void toArray( AnyType [ ] arr )
     {
         Node<AnyType> p = first;

         for( int idx = 0; p != null; idx++, p = p.next )
             arr[ idx ] = p.data;
    }

   (c)
     public void removeLast( )
     {
         if( first == null )
             throw new IllegalStateException( );

         if( first == last )
             first = last = null;
         else
         {
             last = last.prev;
             last.next = null;
         }
     }

   (d)
     public void addFirst( AnyType x )
     {
         if( first == null )
             first = last = new Node<AnyType>( x, null, null );
         else
             first = first.prev = new Node<AnyType>( x, null, first );
     }

3.

   (a)
     public static List<Integer> getPrimes( Map<Integer,List<Integer>> m )
     {
         List<Integer> primes = new ArrayListInteger>( );

         for( Map.Entry<Integer,List<Integer>> e : m.entrySet( ) )
             if( e.getValue( ).size( ) == 1 )
                 primes.add( e.getKey( ) );

         return primes;
     }
             
   (b) This is an O( N ) algorithm
              

4.
     public static int countFiles( File d )
     {
         int count = 1;

         if( d.isDirectory( ) )
             for( File f : d.listFiles( ) )
                 count += countFiles( f );

         return count;
     }