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Solution to CSE142 Sample Final handout #27
1. Expression Value
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(6 + 7)/4/2.0 1.5
13/2 * 3 % 10 - 1 7
30/(2 * 6) + 1.5 3.5
13 % 5 + 5 * 3/4 6
"3 * 4" + 3 * 4 + 10 "3 * 41210"
2. Original List Final List
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(8) (8)
() ()
(3, 0, 1, 4, 7) (3, 0, 4, 8, 19)
(0, 1, 2, 3, 4, 5) (0, 1, 3, 7, 14, 26)
(7, 4, -10, 8, 2) (7, 4, 1, 13, 16)
3. Polymorphism. The output produced is as follows.
squid
creature 1
tentacles
BIG!
spout
creature 2
ocean-dwelling
creature 1
creature 2
ocean-dwelling
warm-blooded
creature 2
4. Token-Based File Processing. One possible solution appears below.
public static void processData(Scanner input) {
int count = 0;
int sum = 0;
while (input.hasNextInt()) {
sum += input.nextInt();
count++;
System.out.println("Sum of " + count + " = " + sum);
}
double average = (double)sum/count;
System.out.println("Average = " + average);
}
5. Line-Based File Processing. One possible solution appears below.
public static void processFile(Scanner input) {
while (input.hasNextLine()) {
String text = input.nextLine();
if (text.length() == 0 || text.charAt(0) != '.')
System.out.println(text);
else {
System.out.println(text.substring(1));
for (int i = 1; i <= text.length() - 1; i++)
System.out.print("-");
System.out.println();
}
}
}
6. Arrays. One possible solution appears below.
public static void printNumber(int[] digits) {
for (int i = 0; i < digits.length; i++) {
if (i > 0 && (digits.length - i) % 3 == 0)
System.out.print(",");
System.out.print(digits[i]);
}
System.out.println();
}
7. ArrayLists. One possible solution appears below.
public static void manyStrings(ArrayList list, int n) {
for (int i = list.size() - 1; i >= 0; i--) {
String target = (String)list.get(i);
for (int j = 0; j < n - 1; j++)
list.add(i, target);
}
}
8. Critters. One possible solution appears below.
public class Ant implements Critter {
private int move;
private int direction1;
private int direction2;
public char getChar() {
return 'A';
}
public int getMove() {
if (this.move % 10 == 0)
if (Math.random() < 0.5) {
this.direction1 = NORTH;
this.direction2 = EAST;
} else {
this.direction1 = SOUTH;
this.direction2 = WEST;
}
int result;
if (this.move % 10 < 5)
result = this.direction1;
else
result = this.direction2;
this.move++;
return result;
}
}
9. Arrays. One possible solution appears below.
public static int[] interleave(int[] list1, int[] list2) {
int[] result = new int[list1.length + list2.length];
int min = Math.min(list1.length, list2.length);
for (int i = 0; i < min; i++) {
result[2 * i] = list1[i];
result[2 * i + 1] = list2[i];
}
for (int i = min; i < list1.length; i++)
result[i + min] = list1[i];
for (int i = min; i < list2.length; i++)
result[i + min] = list2[i];
return result;
}
10. Programming. One possible solution appears below.
public static int indexOf(int[] target, int[] list) {
for (int i = 0; i < list.length - target.length; i++) {
boolean ok = true;
for (int j = 0; j < target.length; j++)
if (list[i + j] != target[j])
ok = false;
if (ok)
return i;
}
return -1;
}
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