#1: Points were deducted if you missed that TreeSet is sorted, if you missed
    that no duplicates should be in the set, or if you did not give me the
    actual print output.

#2: This is in the slides, but the basic three things I wanted folks to address
    were why the n/2 exists, what the if statement is for, and how % plays into
    the solution.

#3: See the slides.

#4: this could be done by removing the leading and trailing whitespace via loop
    but trim() works just fine here

public static boolean isPalindrome(String s){
  s = s.trim();
  if (s.length() == 0 || s.length() == 1)
    return true;
  if (s.charAt(0) == s.charAt(s.length()-1))
    return isPalindrome(s.substring(1, s.length()-1));
  else
    return false;
}

#5: Postfix: 1 2 3 * 5 3 2 ^ ^ / + 4 + 6 7 8 7 8 + ^ * 9 * + -
    Eval: numerous, checked work here
    If you were missing work for either part, you lost points.

#6: 
public class Student{
  public int id; //I do this to save writing space...
  private String name;
  private double gpa;
  
  public Student(){
    id = 0;
    name = "John";
    gpa = 4.0;
  }    

  public Student(int i, String n, double g){
    id = i;
    name = n;
    gpa = g;
  }

  //two methods to ensure HashSet behavior
  //Student ids are generally unique

  public boolean equals(Object s){
    if (s instanceof Student){
      return id == ((Student) s).id;
    }
    return false;
  }

  public int hashCode(){
    return id;
  }
}

#7:
to base 3: 20012
to base 13: 11B