Java find n'th node from the end of linked list 2017-11-29 03:48

public class Node {
    public int data;
    public Node next;

    public Node(int data) {
        this.data = data;
    }
}

public class LinkedList {
    public Node head;
    public Node current;

    private void add(int data) {
        if (head == null) {
            head = new Node(data);
            current = head;
        } else {
            current.next = new Node(data);
            current = current.next;
        }
    }

    public Node init(int length) {
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            this.add(random.nextInt(100));
        }
        return head;
    }

    @Override
    public String toString() {
        if (this.head == null) {
            return "null";
        }
        current = this.head;
        StringBuilder sb = new StringBuilder();
        while (current != null) {
            if (sb.length() != 0) {
                sb.append("->");
            }
            sb.append(current.data);
            current = current.next;
        }
        return sb.toString();
    }
}

public class FindLastNNode {

    public static void main(String[] args) {
        int l = 10;
        int n = 6;
        LinkedList linkedList = new LinkedList();
        linkedList.init(l);
        System.out.println("linked list:" + linkedList);
        Node target = findLastN(linkedList, n);
        System.out.println("the " + n + " node from end:" + target.data);
    }

    private static Node findLastN(LinkedList linkedList, int n) {
        if (linkedList == null || n < 1) {
            return null;
        }
        Node pointer1 = linkedList.head;
        for (int i = 0; i < n; i++) {
            pointer1 = pointer1.next;
        }
        Node pointer2 = linkedList.head;
        while (true) {
            if (pointer1 == null) {
                return pointer2;
            }
            pointer1 = pointer1.next;
            pointer2 = pointer2.next;
        }
    }
}