Code Destine

Problem Statement

You have given a singly linked list and an integer k, rotate the linked list to the right by k places.

Example 

Input :- head = [5, 4, 10, 15, 1], k = 2
Output :- [15, 1, 5, 4, 10]

Input :- head = [0, 1, 2], k = 4
Output :- [2, 0, 1]

Solution

This problem can be solved in the following steps :-

1. Traverse the given linked list, to find out the total number (count) of nodes in the list. If given integer value k is greater than or equal to count, then perform modulus operation on k (k = k % count)
2. If the value of k is greater than zero, then create two variables first and second pointing to the head of the linked list.
3. Move the second variable to the right by k places.
4. Move both first and second variables together, until the second variable reaches last node of the linked list.
5. Assign null to first.next, head to second.next.

Program

public class Main {

	public static void main(String[] args) {
		
		ListNode head = null;
		
		ListNode node = new ListNode(5);
		head = node;		
		node.next = new ListNode(4);
		node = node.next;		
		node.next = new ListNode(10);
		node = node.next;		
		node.next = new ListNode(15);
		node = node.next;		
		node.next = new ListNode(1);
		
		Main main = new Main();
		head = main.rotateRight(head, 2);
		
		ListNode listNode = head;
		while(listNode != null) {
			System.out.print(listNode.value + ", ");
			listNode = listNode.next;
		}
	}
	
	/* Solution */
	public ListNode rotateRight(ListNode head, int k) {
        if(head != null){
            ListNode temp = head;
            int count = 0;
            while(temp != null){
                temp = temp.next;
                count++;
            }

            if(k>=count){
                k = k%count;
            }

            if(k > 0){
                ListNode first = head;
                ListNode second = head;

                while(k>0){
                    second = second.next;
                    k--;
                }

                while(second.next != null){
                    first = first.next;
                    second = second.next;
                }

                temp = first.next;
                first.next = null;
                second.next = head;
                return temp;            
            }
        }
        
        return head;
    }
	
	/* Definition of Linked List Node */
	public static class ListNode {		
		int value;
		ListNode next;
		
		public ListNode(int value) {
			this.value = value;
		}		
	}
}

Result

15, 1, 5, 4, 10,

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