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import java.util.Iterator;
public class LinkedList<T> implements Sequence<T> {
private class ListNode<T> {
T element;
ListNode<T> next;
ListNode(T o) {
element = o;
next = null;
}
void connect(ListNode<T> n) {
next = n;
}
@Override
public String toString() {
return "Value =" + element;
}
}
private class LinkedListIterator implements Iterator<T> {
private int count;
private ListNode<T> node;
LinkedListIterator() {
count = 0;
node = firstNode;
}
public boolean hasNext() {
return count < size();
}
public T next() {
T retVal = node.element;
count++;
node = node.next;
return retVal;
}
}
protected ListNode<T> firstNode;
protected int size;
public LinkedList() {
firstNode = null;
size = 0;
}
public Iterator<T> iterator() {
return new LinkedListIterator();
}
public T get(int index) {
// get head of list, traverse to index using currentNode.next index number of times, return the element at position index
ListNode<T> node = firstNode;
for (int i = 0; i <= index; i++) {
if (i == index) {
return node.element;
} else {
node = node.next;
}
}
return null;
}
public void set(int index, T value) {
ListNode<T> node = firstNode;
for (int i = 0; i <= size; i++) {
if (i == index) {
node.element = value;
break;
} else {
node = node.next;
}
}
}
public void add(int index, T value) {
ListNode<T> newNode = new ListNode<>(value);
if (index == 0) {
if (size == 0) {
firstNode = newNode;
} else {
newNode.connect(firstNode);
firstNode = newNode;
}
} else {
ListNode<T> node = firstNode;
for (int i = 0; i <= index; i++) {
if (i == index - 1) {
newNode.connect(node.next);
node.connect(newNode);
break;
} else {
node = node.next;
}
}
}
size += 1;
}
public T remove(int index) {
ListNode<T> node = firstNode;
T toReturn = firstNode.element;
for (int i = 0; i <= index; i++) {
if (i == index - 1) {
toReturn = node.next.element;
if (i != size() - 2) { // if its the last value, we don't need to link
node.connect(node.next.next);
}
break;
} else {
node = node.next;
}
}
size--;
return toReturn;
}
public void add(T value) {
if (size == 0) {
firstNode = new ListNode<T>(value);
} else {
ListNode<T> node = firstNode;
for (int i = 0; i <= size; i++) {
if (i == size - 1) {
node.connect(new ListNode<T>(value));
break;
} else {
node = node.next;
}
}
}
size += 1;
}
public T remove() {
return remove(size() - 1);
}
public int size() {
return size;
}
public boolean isEmpty() {
return size() == 0;
}
public String toString() {
String s = "["; // better to use a StringBuilder etc.
ListNode<T> currentNode = firstNode;
for (int i = 0; i < size; i++) {
s += currentNode.element.toString() + ", ";
currentNode = currentNode.next;
}
//traverse list, add each eleemnt to s
return s + "]";
}
public LinkedList<T> reverse() {
throw new UnsupportedOperationException("Not supported yet.");
}
// Some basic test methods
public static void main(String[] args) {
LinkedList<String> m = new LinkedList<>();
m.add("First");
m.add("Second");
m.add("Third");
m.add("Fourth");
m.add(0, "Zeroth");
System.out.println(" List is now =\n" + m);
System.out.println(m.remove(4));
System.out.println(" List is now =\n" + m);
// for (String e : m) {
// System.out.println(e);
// }
// //Test Set
// m.set(0, "XXXXX");
// System.out.println("List is now =\n" + m);
// m.set(2, "YYYYY");
// //Test remove
// m.remove(2);
// System.out.println("List is now =\n" + m);
// m.remove(0);
// System.out.println("List is now =\n" + m);
}
}
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