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CSE143X Sample Midterm, Fall 2018 handout #7
1. Expressions, 10 points. For each expression in the left-hand column,
indicate its value in the right-hand column. Be sure to list a constant of
appropriate type (e.g., 7.0 rather than 7 for a double, Strings in quotes).
Expression Value
5 * 6 - (4 + 3) * 2 - 2 * 3 ________________
208 / 20 / 4 + 12 / 10.0 + 0.4 * 2 ________________
8 - 2 + "8 - 2" + 8 * 2 + 8 ________________
4 * 5 % 6 + 297 % 10 + 4 % 8 ________________
13 / 2 * 3.0 + 5.5 * 3 / 2 ________________
2. Parameter Mystery, 12 points. Consider the following program.
public class Mystery {
public static void main(String[] args) {
String x = "lemonade";
String y = "ants";
String z = "picnic";
String picnic = "y";
String ants = x + picnic;
picnic(x, y, z);
picnic(y, picnic, "ants");
picnic(y + z, y + picnic, ants);
picnic = "sunny";
picnic(picnic, "today", x);
}
public static void picnic(String z, String y, String x) {
System.out.println(x + " and " + z + " like " + y);
}
}
List below the output produced by this program.
3. If/Else Simulation, 12 points. Consider the following method.
public static void ifElseMystery(int a, int b) {
if (a > b || a % 2 == 0) {
a++;
b--;
} else if (a % 2 == 1) {
b = 0;
}
if (b == 0 && b != a) {
a = a + 2;
b = a - 2;
}
System.out.println(a + " " + b);
}
For each call below, indicate what output is produced.
Method Call Output Produced
ifElseMystery(5, 20); _______________
ifElseMystery(42, 42); _______________
ifElseMystery(6, 1); _______________
ifElseMystery(2, 0); _______________
ifElseMystery(7, 10); _______________
ifElseMystery(4, 4); _______________
4. While Loop Simulation, 12 points. Consider the following method:
public static void mystery(int y) {
int x = 0;
int z = 0;
while (y > 0) {
x++;
z = z + y % 10;
y = y / 10;
}
System.out.println(x + " " + z);
}
For each call below, indicate what output is produced.
Method Call Output Produced
mystery(8); _______________
mystery(32); _______________
mystery(184); _______________
mystery(8239); _______________
5. Assertions, 15 points. You will identify various assertions as being either
always true, never true or sometimes true/sometimes false at various points
in program execution. The comments in the method below indicate the points
of interest.
public static void mystery(Scanner console) {
int y = 42;
int z = 0;
// Point A
while (y != 0) {
// Point B
y = console.nextInt();
if (y % 2 == 0) {
z++;
// Point C
y--;
}
// Point D
y--;
}
// Point E
System.out.println("z = " + z);
}
Fill in the table below with the words ALWAYS, NEVER, or SOMETIMES (you may
abbreviate them as A, N, or S).
y == 0 y % 2 == 0 z == 0
+---------------------+---------------------+---------------------+
Point A | | | |
+---------------------+---------------------+---------------------+
Point B | | | |
+---------------------+---------------------+---------------------+
Point C | | | |
+---------------------+---------------------+---------------------+
Point D | | | |
+---------------------+---------------------+---------------------+
Point E | | | |
+---------------------+---------------------+---------------------+
6. Programming, 10 points. Write a static method called printSequenceTo that
takes a target value as a parameter and that prints terms from a particular
numerical sequence until they add up to a value greater than or equal to the
target and that returns the number of terms that were included. For
example, if the following calls are made:
int n1 = printSequenceTo(3.0);
int n2 = printSequenceTo(5.5);
The following output should be produced:
1/2 + 2/3 + 3/4 + 4/5 + 5/6 = 3.5500000000000003
1/2 + 2/3 + 3/4 + 4/5 + 5/6 + 6/7 + 7/8 + 8/9 = 6.171031746031746
The variable n1 is set to 5 because it took 5 terms from the sequence to get
a sum that is at least 3.0. The variable n2 would be set to 8 because it
took 8 terms to get a sum that is at least 5.5. You are to exactly
reproduce the format of this output. You may assume that the target is
greater than 0. Notice that the sum is not rounded.
7. File Processing, 10 points. Write a static method called switchData that
takes as a parameter a Scanner containing an input file of labeled data and
that prints the same information with successive pairs of numbers on each
line switched in order. Each line of the input file will consist of a label
followed by a sequence of integers. For example, if a variable called input
refers to the following file:
Karen 1 2 3 4 5 6
Sam 38 14 79 4 -3
42 2 4 6 8 12
extras
anon 15
then the call:
switchData(input);
would produce the following output:
Karen 2 1 4 3 6 5
Sam 14 38 4 79 -3
42 4 2 8 6 12
extras
anon 15
The first line of the file has the label "Karen" followed by 6 integers.
Notice that the first pair of integers (1, 2) has been switched (2, 1), and
the second pair of integers (3, 4) has been switched (4, 3), and so on.
This first example involved sequential integers to make the switching more
obvious, but this won't always be the case. You also shouldn't assume that
you have an even number of integers. If there is an odd number of integers,
as in the second line of input, then the final value should not be moved
(the -3 appears at the end in both input and output).
There will always be a one-word label (possibly a number as in the example
of "42"), but the list of integers might be empty, in which case the method
simply prints the label on a line by itself (as in the example of "extras").
You may assume that the input is legal (a sequence of lines each with a
one-word label followed by 0 or more integer values). You may not construct
any extra data structures to solve this problem other than Scanner objects.
8. Arrays, 10 points. Write a static method called minToFront that takes an
array of integers as a parameter and that moves the minimum value in the
list to the front by swapping its position with whatever is currently at the
front of the list. For example, if a variable called list stores the
following values:
[3, 8, 92, 4, 2, 17, 9]
and you make the following call:
minToFront(list);
The value 2 is the minimum, so the list should store the following values
after the call:
[2, 8, 92, 4, 3, 17, 9]
Notice that the value 3 which used to be at the front of the list is now at
index 4 where the value 2 was before. If there is more than one occurrence
of the minimum value, your method should move the first occurrence to the
front of the list. If the minimum value is already at the front of the
array or if the array is empty, then the array should be unchanged after the
method executes.
You may not construct any extra data structures to solve this problem (not
even a string).
9. Programming, 9 points. Write a static method called isMatch that takes a
pattern string and a target string as parameters and that returns whether or
not the given target matches the pattern. Patterns can contain special
wildcard characters dot (".") and star ("*"). If a pattern does not contain
any wildcards, then the target has to be the same string, as in
isMatch("and", "and"). A dot can match any single character. For example,
the pattern "a.." matches any 3-letter string beginning with the letter "a".
A star can match any sequence of characters (including no characters). For
example, the pattern "a*t" matches any string that begins with "a" and ends
with "t", including "at". There will be at most one star in any given
pattern, although a pattern can contain several dots and a star. Below are
examples of patterns and matching strings (note that your method compares a
pattern against a single string, not a list of strings).
Pattern Matching strings
--------- -----------------------------------------------------
"hello" hello
"..." and, ant, but, cat, cow, hat, sat, tap, ten, the, tot
"a..." atom, army, aunt, aura
".a.." bats, task, yard, saga, lava
"...a" tuna, soda, coma, aura, saga, lava
"....th" growth, zenith, health
"a*" a, an, at, and, ant, atom, aunt, apple, army, aura
"t*t" tot, that, trot, tiniest
"the*" the, then, there, therefore, thermal, thespians
".a*a" saga, lava, saliva, tarantula, nausea
"t.e.p*" twerp, trespass, thespians
".o*e." poem, token, wolves, voucher, toothbrushes
You are allowed to create new strings, but otherwise you are not allowed to
construct extra data structures to solve this problem (no array, ArrayList,
Scanner, etc). You are limited to the string methods listed on the cheat
sheet (otherwise this problem can be solved in one line of code).
You can receive up to 4 points for a solution that handles the dot wildcard
without handling the star wildcard. If you wish to pursue this option,
please mark the box below:
+---+
| | I agree to limit my score to 4 by handling just the dot wildcard
+---+
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