Problem 1: Number Repsentations

  -- what got some people on this was reading B as if it were an integer.
     B is expressed as a binary string, but that doesn't mean your 
     program will read it as a binary string.  Some solutions tried to read
     it as an integer, which failed since B could have up to 30 digits.

Problem 2: Banker's Rounding

  -- You have to worry about 2 things.  1) floats and doubles are horribly
     imprecise.  You're probably better off using a string and manipulating
     the results.  2) Be careful of carries.  9.9951 rounds to 10.00.

Problem 3: Land Inheritance

  -- compute the convex hull and then run around the points computing area.
     there's more notes in the solution file.

Problem 4: Valid Sudoku Boards

  -- Failures seemed to pop up by not checking the conditions in the order
     specified (all rows first, then all columns, then the regions).  
     Some gave 0 for a row or column number, which is invalid by the
     problem spec.

Problem 5: Finite Automatons

Problem 6: Batting Stats

   -- This problem was more subtle than it initially appears.  The problem
      is that you can have a perfect average, slugging percentage, or
      on base percentage.  The judge input had a case where the hitter
      recorded one plate appearance, no at bats, 1 walk.  That's an OBP
      of 1.000.  Alot of submissions missed the 1 part.  I sent out a
      clarification to try and clear things up about that (but I didn't
      want to give it all away).