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Key to CSE143X Midterm, Fall 2021 handout #11
1. Expression Value
-----------------------------------------------
13 + 2 * 5 / 3 16
2.5 * 2 * 5 / 10 + 1.5 4.0
85 % 10 + 4 % 10 - 17 % 3 7
2 + 3 + "." + (3 + 4) + 2 * 3 "5.76"
482 / 10 / 5 / 2.0 * 2 + 14 / 5 11.0
2. Parameter Mystery. The program produces the following output.
a snow and slippery for sleet
a storm and snow for sleetsnow
a snowsleet and sleetsnow for snowstorm
a sun and storm for sunny
3. Method Call Output Produced
---------------------------------------
ifElseMystery(2, 5); 4 2
ifElseMystery(5, 5); 10 20
ifElseMystery(6, 3); 3 13
ifElseMystery(4, 4); 8 9
ifElseMystery(3, 8); 5 15
ifElseMystery(9, 5); 6 5
4. Method Call Output Produced
---------------------------------------
mystery(4); 2 2
mystery(5); 1 5
mystery(24); 4 3
mystery(28); 3 7
5. x == 1 x % 2 == 1 y == 0
+---------------------+---------------------+---------------------+
Point A | sometimes | sometimes | always |
+---------------------+---------------------+---------------------+
Point B | never | sometimes | sometimes |
+---------------------+---------------------+---------------------+
Point C | sometimes | sometimes | never |
+---------------------+---------------------+---------------------+
Point D | never | never | sometimes |
+---------------------+---------------------+---------------------+
Point E | always | always | sometimes |
+---------------------+---------------------+---------------------+
6. One possible solution appears below.
public static int generate(Scanner console) {
System.out.print("number between -5 and 5? ");
int target = console.nextInt();
Random r = new Random();
int next = r.nextInt(11) - 5;
System.out.print("numbers are: " + next);
int count = 1;
while (next != target) {
next = r.nextInt(11) - 5;
System.out.print(", " + next);
count++;
}
System.out.println();
System.out.println("came up after " + count + " tries");
return count;
}
7. One possible solution appears below.
public static void switchNames(Scanner input) {
while (input.hasNextLine()) {
String line = input.nextLine();
if (line.equals("name:")) {
String line2 = input.nextLine();
int commaIndex = line2.indexOf(",");
String last = line2.substring(0, commaIndex);
String first = line2.substring(commaIndex + 2);
System.out.println(first + " " + last);
} else {
System.out.println(line);
}
}
}
8. Arrays. One possible solution appears below.
public static boolean isAllPairs(int[] list) {
if (list.length % 2 == 1) {
return false;
}
for (int i = 1; i < list.length; i += 2) {
if (list[i] != list[i - 1]) {
return false;
}
}
return true;
}
9. 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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