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Key to CSE143X Midterm, Autumn 2025 handout #17
1. Method Call Output Produced
------------------------------------------------
mystery(7); 7
mystery(38); 3, 2
mystery(749); 7, 1, 0
mystery(-6842); 6, 2, 1, 2
mystery(954023); 9, 2, 1, 0, 2, 0
2. One possible solution appears below.
public int weave(int x, int y) {
if (x < 0 || y < 0) {
throw new IllegalArgumentException();
}
if (x == 0 && y == 0) {
return 0;
} else {
return 100 * weave(x / 10, y / 10) + 10 * (x % 10) + y % 10;
}
}
3. Statement Output
------------------------------------------------------------
var1.method2(); compiler error
var2.method2(); Bunch 2/Bunch 3
var3.method2(); Bunch 2/Bit 3
var4.method2(); Bunch 2/Page 3
var5.method2(); compiler error
var6.method2(); Bunch 2/Page 3
var1.method3(); compiler error
var2.method3(); Bunch 3
var3.method3(); Bit 3
var4.method3(); Page 3
var5.method3(); compiler error
var6.method3(); Page 3
((Bit)var6).method1(); runtime error
((Bunch)var1).method1(); compiler error
((Bunch)var1).method2(); Bunch 2/Folder 3/Bunch 3
((Folder)var1).method3(); Folder 3/Bunch 3
((Folder)var6).method1(); Folder 1
((Page)var1).method1(); runtime error
((Page)var4).method2(); Bunch 2/Page 3
((Folder)var3).method1(); runtime error
4. before after code
-----------------------+-----------------------+-------------------------------
p->[1]->[2]->[3] | p->[1]->[2] | q = p.next.next;
| | p.next.next = null;
q | q->[3] |
-----------------------+-----------------------+-------------------------------
p->[1]->[3] | p->[1]->[2]->[3] | q.next = p.next;
| | p.next = q;
q->[2] | q | q = null;
-----------------------+-----------------------+-------------------------------
p->[1]->[2] | p->[2]->[4] | p.next.next = q.next;
| | q.next = p;
q->[3]->[4] | q->[3]->[1] | p = p.next;
| | q.next.next = null;
-----------------------+-----------------------+-------------------------------
p->[1]->[2]->[3] | p->[2]->[1]->[4] | p.next.next.next = q.next;
| | ListNode temp = q;
q->[4]->[5] | q->[3]->[5] | q = p.next.next;
| | p.next.next = p;
| | p = p.next;
| | p.next.next = temp;
| | temp.next = null;
-----------------------+-----------------------+-------------------------------
5. One possible solution appears below.
public ArrayIntList reverseCopy() {
ArrayIntList result = new ArrayIntList(elementData.length);
for (int i = 0; i < size; i++) {
result.elementData[i] = elementData[size - 1 - i];
}
result.size = size;
return result;
}
6. One possible solution appears below.
public void mirror(Stack<Integer> s) {
Queue<Integer> q = new LinkedList<Integer>();
while (!s.isEmpty()) {
q.add(s.pop());
}
while (!q.isEmpty()) {
s.push(q.remove());
}
while (!s.isEmpty()) {
q.add(s.pop());
}
for (int i = 0; i < q.size(); i++) {
int n = q.remove();
s.push(n);
q.add(n);
}
while (!s.isEmpty()) {
q.add(s.pop());
}
while (!q.isEmpty()) {
s.push(q.remove());
}
}
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