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Problem #1:
2 pts each, 1 pt for correct value of wrong type (missing parens, no .0)
Problem #2:
1 pt for each of the 12 values
-1 if any error in surrounding text (dittos not allowed)
-4 if two columns transposed
-8 if you need to transpose twice
Problem #3:
-2 if columns transposed
each is 3 pts, -1 for a single number wrong or for a single transpose
Problem #4:
-3 if fibonacci sequence is one off (e.g., 1, 1, 3, 8)
Problem #6
Solution:
public static int quadrant(double x, double y) {
if (x > 0 && y > 0) {
return 1;
} else if (x < 0 && y > 0) {
return 2;
} else if (x < 0 && y < 0) {
return 3;
} else if (x > 0 && y < 0) {
return 4;
} else { // at least one equals 0
return 0;
}
}
2 correct header (void okay if no return, -1 per error, int/int vs
double/double types for x and y is one error)
3 they return the values they compute
2 most of the time
1 always
10 five different cases
2 quadrant 1 (x > 0 && y > 0)
1 attempt (specifically try to test for this case)
1 correct (correct test, always returns 1 in this case)
2 quadrant 2 (x < 0 && y > 0)
1 attempt (specifically try to test for this case)
1 correct (correct test, always returns 2 in this case)
2 quadrant 3 (x < 0 && y < 0)
1 attempt (specifically try to test for this case)
1 correct (correct test, always returns 3 in this case)
2 quadrant 4 (x > 0 && y < 0)
1 attempt (specifically try to test for this case)
1 correct (correct test, always returns 4 in this case)
2 quadrant 0 (x == 0 || y == 0)
1 attempt (specifically try to test for this case)
1 correct (correct test, always returns 0 in this case)
** Special Cases **
-1 if return a String instead of int (can get header return type
if it returns String)
-1 per swap e.g. if quadrant 4 and 2 are backwards
-1 for 1's instead of 0's
-1 for <= or >=
-2 scope issues
Problem #7
Solution:
public static void printTwoDigit(Random r, int n) {
boolean seen42 = false;
for (int i = 1; i <= n; i++) {
int number = r.nextInt(90) + 10;
System.out.println("next = " + number);
if (number == 42) {
seen42 = true;
}
}
if (seen42) {
System.out.println("We saw a 42");
} else {
System.out.println("no 42");
}
}
1 header
4 for loop
2 attempt
2 correct (-1 if OBOB)
3 choosing random 2-digit number
1 attempt
2 correct (-1 if OBOB)
2 println inside the loop to print 2-digit number
1 attempt
1 correct
5 Did we see a 42?
1 two printlns ("We saw a 42" and "no 42")
2 some kind of flag or counter variable that is updated when 42 is seen
(exception: -1 for small mistakes, such as checking for 24 instead of 42)
1 correct initialization of that counter/flag
1 counter/flag variable used correctly with an if/else or if/if after the
loop to choose between the two printlns
-1 for incorrectly using Random object
Problem #8
Solution:
public static int digitsInARow(int n) {
int count = 1;
int last = -1;
int max = 1;
while (n > 0) {
if (n % 10 == last) {
count++;
} else {
count = 1;
}
if (count > max) {
max = count;
}
last = n % 10;
n = n / 10;
}
return max;
}
Plus criteria (max +4)
1 header
2 loop that uses n/10 and n%10 to pull apart the digits of a number
1 attempt
1 correct
1 counter variable with at least 2 of:
initialized to 0 before loop
attempt to increment inside loop
returned after loop
-------------------------------------------------------------------------------
Minus Criteria (min of 5)
To grade this way, you have to see a loop that pulls apart digits and a counter
AND a reasonable attempt to compare adjacent digits. These include:
storing a prev digit to compare against
checking to see if last 2 digits are divisible by 11
checking to see if (ones digit == tens digit)
When in doubt, pass along a solution for minus grading.
Minus grading starts at 9 and works down, never going below 5.
-1 for minor error (bad initialization, forgot to return)
-2 for medium error (printing result rather than returning, doesn't handle
sequences at end of number)
-3 for major error (counts all occurrences of a digit vs "in a row")
-4 if no max computation (counts all digit matches or counts last match)
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Stuart Reges
Last modified: Fri Sep 16 15:55:02 PDT 2011