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class LinkedList {
class Node { double item; Node next; }
Node first;
public double sum1 () {
double result = 0;
Node current = first; // may be null
while (current != null) {
result = result + current.item;
current = current.next;
}
}
public double sum2 () {
if (first == null) return 0;
double result = first.item;
Node prev = first; // never null
while (prev.next != null) {
result = result + prev.next.item;
prev = prev.next;
}
}
public double sum3 () {
if (first == null) return 0;
double result = first.item;
Node prev = first; // never null
Node current = first.next; // may be null
while (current != null) {
result = result + current.item;
prev = prev.next;
current = current.next;
}
}
}
public static double sum (double[] a) {
double result = 0;
int i = 0;
while (i<a.length) {
result = result + a[i];
i = i + 1;
}
}
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