// CSE 143, winter 2012
// A LinkedIntList object is a list of integers represented as linked nodes.
// LinkedIntList implements the same methods as ArrayIntList but with
// different runtime efficiencies.
public class LinkedIntList {
	private ListNode front;
	
	// Constructs an empty list
	public LinkedIntList() {
		front = null;
	}
	
	// Add the given value to the end of the list.
	public void add(int value) {
		if (front == null) {
			front = new ListNode(value);
		} else {
			// list wasn't empty; find the back
			// (note: this is inefficient.  We could keep a reference to the last node)
			ListNode current = front;
			while (current.next != null) {
				current = current.next;
			}
			current.next = new ListNode(value);
		}
	}
	
	// Returns the value at a given index.
	// Pre: 0 <= index < size
	// Throws a NullPointerException if index > size. 
	public int get(int index) {
		ListNode current = front;
		for (int i = 0; i < index; i++) {
			current = current.next;
		}
		return current.data;
	}
	
	// Adds a value at a given index.
	// Pre: 0 <= index <= size
	// Throws a NullPointerException if index > size. 
	public void add(int index, int value) {
		if (index == 0) {
			front = new ListNode(value, front);
		} else {
			ListNode current = front;
			for (int i = 0; i < index - 1; i++) {
				current = current.next;
			}
			current.next = new ListNode(value, current.next);
		}
	}
}