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Key to CSE142 Sample Midterm, Fall 2017
1. Expression Value
-----------------------------------------------
5 * 6 - (4 + 3) * 2 - 2 * 3 10
208 / 20 / 4 + 12 / 10.0 + 0.4 * 2 4.0
8 - 2 + "8 - 2" + 8 * 2 + 8 "68 - 2168"
4 * 5 % 6 + 297 % 10 + 4 % 8 13
13 / 2 * 3.0 + 5.5 * 3 / 2 26.25
2. Parameter Mystery. The program produces the following output.
table and chair like notes
notes and notes like x
notesx and notestable like notesx
chair and boring like today
3. Method Call Output Produced
---------------------------------------
ifElseMystery(6, 5); 5 15
ifElseMystery(4, 6); 7 5
ifElseMystery(9, 5); 7 15
ifElseMystery(3, 6); 5 5
ifElseMystery(2, 7); 8 6
ifElseMystery(1, 3); 3 13
4. Method Call Output Produced
---------------------------------------
mystery(5); 0 0
mystery(28); 2 82
mystery(346); 2 64
mystery(265408); 3 804
5. x > 0 x == 0 y == 0
+---------------------+---------------------+---------------------+
Point A | always | never | always |
+---------------------+---------------------+---------------------+
Point B | always | never | sometimes |
+---------------------+---------------------+---------------------+
Point C | never | never | never |
+---------------------+---------------------+---------------------+
Point D | never | sometimes | never |
+---------------------+---------------------+---------------------+
Point E | never | always | never |
+---------------------+---------------------+---------------------+
6. One possible solution appears below.
public static void printSum(int n, int low, int high) {
System.out.println("sum " + n + " numbers " + low + " to " + high);
Random r = new Random();
int next = r.nextInt(high - low + 1) + low;
int max = next;
int sum = next;
System.out.print(next);
for (int i = 2; i <= n; i++) {
next = r.nextInt(high - low + 1) + low;
System.out.print(" + " + next);
sum = sum + next;
if (sum > max) {
max = sum;
}
}
System.out.println(" = " + sum);
System.out.println("max = " + max);
}
6. Programming. Two possible solutions appear below:
public static double tallyVotes(Scanner input) {
System.out.print("vote? ");
String vote = input.next();
double result = 0;
int total = 0;
while (!vote.equals("q")) {
if (vote.equals("y")) {
result++;
}
total++;
System.out.print("vote? ");
vote = input.next();
}
result = result / total * 100;
System.out.println("total votes = " + total);
System.out.println("result = " + result + "%");
return result;
}
public static double tallyVotes(Scanner input) {
String vote = "";
int yes = 0;
int no = 0;
while (!vote.equals("q")) {
System.out.print("vote? ");
vote = input.next();
if (vote.equals("y")) {
yes++;
} else if (vote.equals("n")) {
no++;
}
}
int total = yes + no;
double result = 100.0 * yes / total;
System.out.println("total votes = " + total);
System.out.println("result = " + result + "%");
return result;
}
8. Two possible solutions appear below.
public static String undouble(String s) {
String result = "";
if (s.length() > 0) {
char last = s.charAt(0);
result += last;
for (int i = 1; i < s.length(); i++) {
if (s.charAt(i) != last) {
result += s.charAt(i);
}
last = s.charAt(i);
}
}
return result;
}
public static String undouble(String s) {
String result = "";
if (s.length() > 0) {
result = s.substring(0, 1);
for (int i = 1; i < s.length(); i++) {
if (s.charAt(i) != s.charAt(i - 1)) {
result += s.charAt(i);
}
}
}
return result;
}
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