Leetcode problem 19 Remove Nth node from end of the list.txt

LeetCode Problem 19: Remove Nth Node from the end of Linked List

Given a linked list, remove the n-th node from the end of list and return its head.

Example:

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.
Note:

Given n will always be valid.

Follow up:

Could you do this in one pass?



HINT TO SOLVE: two pointer solution. Rabbit and turtle method.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode RemoveNthFromEnd(ListNode head, int n) 
    {
        ListNode leftPointer = new ListNode(0);
        leftPointer.next = head;
        
        ListNode rightPointer = null;
        ListNode temp = head;
        
        for(int i = 0; i<n-1; ++i)
        {
            temp = temp.next;
        }
        
        rightPointer = temp;
        
        Console.WriteLine("Left: "+leftPointer.val +" "+ "RightValue "+ rightPointer.val);
        
        while(rightPointer.next != null)
        {
            leftPointer = leftPointer.next;
            rightPointer = rightPointer.next;
        }
        
        Console.WriteLine("Left: "+ leftPointer.val +" RightValue: "+ rightPointer.val);
        
        
        if(rightPointer == head)
        {
            head = null;
        }
        else if(leftPointer.next == head)
        {
            head = head.next;
        }
        else
        {
            leftPointer.next = leftPointer.next.next;
        }
        
        
        return head;
       
    }
}