LC 19. Remove Nth Node From End of List - optimal.txt

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */

class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode start = new ListNode();
        start.next = head;
        ListNode right = start;
        ListNode left = start;

        for(int i=0; i<n; i++)
        {
            right = right.next;
        }
        while(right.next != null)
        {
            right = right.next;
            left = left.next;
        }
        left.next = left.next.next;

        return start.next;
    }
}
// TC: O(n), SC: O(1)