CS 211, Spring 2005
Prelim 1 grading guide

 Question 1: Induction
=======================
 Base Case 5 points
    1 for the label
    4 for proving n=0 correctly
       -1 if they plugged a value into the sum from 0 to -1. 
 Inductive Hypothesis 3 points
    -2 if they said for all n
    -1 if they didn't label it
    -1 if they didn't say n >= 0
    (up to 3 points off)
 Inductive Step 3 points
    Must have used it correctly
    -1 if they didn't label it
 Algebra 2 points
    -2 if messed up algebra very badly
    -1 for minor algebra mistake
 Conclusion 2 points
    1 for the label
    1 for a satisfactory conclusion

Common mistakes
    - tried to evaluate the sum from 0 to -1.
    - forgot the conclusion
    - didn't assume for some n >= 0

 Question 2:
=============

Each subpart was awarded 3 points as follows:

(a) 3 for "abcde"
    0 otherwise
(b) 3 for "not equal"
    0 otherwise
(c) 3 for "hello"
    0 otherwise
(d) 3 for "012"
    1 for "123"
    0 otherwise
(e) 3 for "32"
    0 otherwise
(f) 3 for "4"
    0 otherwise
(g) 3 for "VbnC"
    0 otherwise
(h) 3 for "12 13"
    1 for "12 12"
    1 for "13 13"
    0 otherwise

 Question 3:
=============

(a) 2.5 points for stating that a reference is a pointer
    1   point if an example of pointer semantics is given with no/invalid
        explanation

    2.5 points for stating that primitive types store data directly
    1   point for an example or primitive type semantics with no/invalid
        explanation

(b) 2.5 points for stating that static type is known at compile time
    1   point for an example, without a valid explanation

    2.5 points for stating that the dynamic type is the type of an object at
        runtime
    1   point for an example, without a valid explanation

Common mistakes:
 - only saying that a primitive type uses less memory than a reference type
 - describing static variables, rather than static types.

 Question 4:
=============

5 points for checking for a null (i.e. empty) tree
  (-2) if only the children are checked (i.e. if tree2list(null) fails)

5 points for traversing the tree in preorder

5 points for properly building and maintaining the list
  (-2.5) for losing the tail

Common mistakes:
 - many people had code that simply didn't make sense.  For those, we did our
   best to award points where we could.

 Question 5:
=============

1 point each.

 Question 6:
=============

3 points for checking that the input is a String.
3 points for casting the input to a String after the dynamic check
  if try/catch is used for these, only three points are awarded.
3 points for checking that the lengths are the same (this may be implicit in
  the loop)
6 points for the loop:
  1 point for the loop construct itself
  4 points for charAt comparison, -1 point if compareTo or equals is used for
    character comparison
  1 point for the logic of the loop
1 point for general correctness
  - 1 for syntax error or scoping error