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Key to CSE143X Midterm, Fall 2020 handout #11
1. Expression Value
-----------------------------------------------
3 * (5 - 2) - 3 - 2 * 2 2
4 * 7 % 8 + 132 % 10 + 3 % 4 9
27 / 5 / 2 + 3.4 * 2 - 1.1 * 2 6.6
9 + 9 + "9 + 9" + 9 + 9 "189 + 999"
19 / 2 / 2.0 + 2.5 * 6 / 2 + 0.5 * 4 14.0
2. Parameter Mystery. The program produces the following output.
semi missing brace and a 42
semi missing 42 and a 8
brace missing literal and a semi
84 missing 1 and a cse
3. Method Call Output Produced
---------------------------------------
ifElseMystery(6, 5); 5 15
ifElseMystery(2, 2); 4 2
ifElseMystery(3, 1); 1 4
ifElseMystery(4, 0); 4 1
ifElseMystery(5, 3); 4 7
ifElseMystery(1, 2); 2 0
ifElseMystery(7, 4); 8 7
4. Method Call Output Produced
---------------------------------------
mystery(1); 1 1
mystery(5); 3 4
mystery(10); 4 8
mystery(42); 6 32
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 spinWheel(Random r, int n) {
int spin = r.nextInt(5) * 10 + 20;
System.out.print("spins: " + spin);
int count = 0;
if (spin == 20) {
count++;
}
int totalSpins = 1;
while (count < n) {
spin = r.nextInt(5) * 10 + 20;
totalSpins++;
System.out.print(", " + spin);
if (spin == 20) {
count++;
} else {
count = 0;
}
}
System.out.println();
System.out.println(n + " in a row after " + totalSpins + " spins");
}
7. One possible solution appears below.
public static void printFigure(Scanner input) {
while (input.hasNextLine()) {
String line = input.nextLine();
Scanner data = new Scanner(line);
while (data.hasNextInt()) {
int count = data.nextInt();
String text = data.next();
for (int i = 0; i < count; i++) {
if (text.equals("space")) {
System.out.print(" ");
} else {
System.out.print(text);
}
}
}
System.out.println();
}
}
8. Arrays. One possible solution appears below.
public static int numUnique(int[] list) {
if (list.length == 0) {
return 0;
} else {
int count = 1;
for (int i = 1; i < list.length; i++) {
if (list[i] != list[i - 1]) {
count++;
}
}
return count;
}
}
9. Two possible solutions appear below.
public static int numWords(String s) {
int count = 0;
boolean inWord = false;
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == ' ') {
inWord = false;
} else if (!inWord) {
count++;
inWord = true;
}
}
return count;
}
public static int numWords(String s) {
int count = 0;
for (int i = 1; i < s.length(); i++) {
if (s.charAt(i - 1) == ' ' && s.charAt(i) != ' ') {
count++;
}
}
if (s.length() > 0 && s.charAt(0) != ' ') {
count++;
}
return count;
}
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