COMP1010 Week 11 Recursive Data Structure - SubList Method

create sublist from linked list

public static Node subList(Node start, int idx1, int idx2) {
		int length = getLength(start, 0); //how many items
		if(!isValidIdx(length, idx1, idx2) || start == null) {
			return null;
		}		
		Node temp = get(new Node(start.data, start.next), idx1); //get item at index
		
		return subList(temp, (idx2-idx1+1));
	}
	
	/***
	 * 
	 * @param start
	 * @param numItems
	 * @return a linked list with "numItems" amount of items
	 */
	public static Node subList(Node start, int numItems) {
		if(numItems <= 0) { //end of list
			return null;
		}
		Node temp = new Node(start.data); //create new item
		temp.next = subList(start.next, numItems -1); //get the next item
		return temp; //once done, return that first node back to the caller function
		
	}
	
	/***
	 * 
	 * @param head - first node in the list
	 * @param length - counter for how many items there are
	 * @return the number of items in the linked list
	 */
	public static int getLength(Node head, int length) {
		if(head != null) {
			return getLength(head.next, length+1);
		}
		return length;
	}
	
	/***
	 * 
	 * @param l - number of items in the list
	 * @param idx1
	 * @param idx2
	 * @return if the range provided by idx1 and idx2 is valid for a list of size l
	 */
	public static boolean isValidIdx(int l, int idx1, int idx2) {
		return idx1 >= 0 && idx1 <= idx2 && idx2 < l;
	}