Linked Lisst -k Append

#1

test case 3 is giving run-error
public void appendLastN(int n) throws Exception {
n=n%size;
if(n<0)
{throw new Exception(“bhuk”);}
if(n==size)
{return;}
Node c= head;
Node p=null;
int k = size-n;
for(int i=0 ; i<k ; i++)
{
p=c;
c=c.next;
}
p.next=null;
Node t=c;
while(t.next!=null)
{t=t.next;}
t.next=head;
head=c;
}

the whole code:-
import java.util.*;
public class LinkedList {
private class Node {
int data;
Node next;

	Node(int data, Node next) {
		this.data = data;
		this.next = next;
	}
}

private Node head;
private Node tail;
private int size;

public LinkedList() {
	this.head = null;
	this.tail = null;
	this.size = 0;
}

public LinkedList(Node head, Node tail, int size) {
	this.head = head;
	this.tail = tail;
	this.size = size;
}

// O(1)
public int size() {
	return this.size;
}

// O(1)
public boolean isEmpty() {
	return this.size() == 0;
}

// O(1)
public int getFirst() throws Exception {
	if (this.isEmpty()) {
		throw new Exception("List is empty.");
	}

	return this.head.data;
}

// O(1)
public int getLast() throws Exception {
	if (this.isEmpty()) {
		throw new Exception("List is empty.");
	}

	return this.tail.data;
}

// O(N)
public int getAt(int idx) throws Exception {
	Node temp = this.getNodeAt(idx);
	return temp.data;
}

// O(N)
private Node getNodeAt(int idx) throws Exception {
	if (this.isEmpty()) {
		throw new Exception("List is empty");
	}

	if (idx < 0 || idx >= this.size()) {
		throw new Exception("Invalid arguments");
	}

	Node retVal = this.head;
	for (int i = 0; i < idx; i++) {
		retVal = retVal.next;
	}

	return retVal;
}

// O(1)
public void addFirst(int data) {
	Node node = new Node(data, this.head);

	if (this.size() == 0) {
		this.head = node;
		this.tail = node;
	} else {
		this.head = node;
	}

	this.size++;
}

// O(1)
public void addLast(int data) {
	Node node = new Node(data, null);

	if (this.size() == 0) {
		this.head = node;
		this.tail = node;
	} else {
		this.tail.next = node;
		this.tail = node;
	}

	this.size++;
}

// O(n)
public void addAt(int idx, int data) throws Exception {
	if (idx < 0 || idx > this.size()) {
		throw new Exception("Invalid arguments");
	}

	if (idx == 0) {
		this.addFirst(data);
	} else if (idx == this.size()) {
		this.addLast(data);
	} else {
		Node nm1 = this.getNodeAt(idx - 1);
		Node n = nm1.next;

		Node node = new Node(data, n);
		nm1.next = node;

		this.size++;
	}
}

// O(1)
public int removeFirst() throws Exception {
	if (this.isEmpty()) {
		throw new Exception("List is empty");
	}

	int retVal = this.head.data;

	if (this.size() == 1) {
		this.head = null;
		this.tail = null;
	} else {
		this.head = this.head.next;
	}

	this.size--;
	return retVal;
}

// O(n)
public int removeLast() throws Exception {
	if (this.isEmpty()) {
		throw new Exception("List is empty");
	}

	int retVal = this.tail.data;

	if (this.size() == 1) {
		this.head = null;
		this.tail = null;
	} else {
		Node sm2 = this.getNodeAt(this.size() - 2);
		sm2.next = null;
		this.tail = sm2;
	}

	this.size--;
	return retVal;
}

// O(n)
public int removeAt(int idx) throws Exception {
	if (this.isEmpty()) {
		throw new Exception("List is empty");
	}

	if (idx < 0 || idx >= this.size()) {
		throw new Exception("Invalid arguments");
	}

	if (idx == 0) {
		return this.removeFirst();
	} else if (idx == this.size() - 1) {
		return this.removeLast();
	} else {
		Node nm1 = this.getNodeAt(idx - 1);
		Node n = nm1.next;
		Node np1 = n.next;

		nm1.next = np1;
		this.size--;

		return n.data;
	}
}

// O(n)
public void display() {
	Node node = this.head;

	while (node != null) {
		System.out.print(node.data + " ");
		node = node.next;
	}

	//System.out.println("END");
}
public void appendLastN(int n) throws Exception {
    n=n%size;
    if(n<0)
    {throw new Exception("bhuk");}
    if(n==size)
    {return;}
    Node c= head;
    Node p=null;
   int k = size-n;
    for(int i=0 ; i<k ; i++)
    {
        p=c;
        c=c.next;
    }
    p.next=null;
    Node t=c;
    while(t.next!=null)
    {t=t.next;}
    t.next=head;
    head=c;

}
public static void main(String[] args) throws Exception {

	Scanner scn = new Scanner(System.in);
	int N = scn.nextInt();
	//int M = scn.nextInt();

	
	LinkedList list = new LinkedList();

	for (int i = 0; i < N; i++) {
		list.addLast(scn.nextInt());
	}
	int n= scn.nextInt();
	list.appendLastN(n);
	list.display();

}
}

#2

please provide your ide link of the code. I’m not able to correct your code here
Also, did you check the case when k>n?

#3

One simple approach can be to make the list as a circular linked list by attaching the last node’s pointer to the first, and then making the pointer of kth node from the end (n-kth node from start) point to null. Update head and tail. This will give the correct answer

#4

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