[LeetCode] 19. Remove Nth Node From End of List

 

 

 

https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/

 

public class Solution
{
    public ListNode RemoveNthFromEnd(ListNode head, int n)
    {
        int nodeCount = 0;

        var current = head;
        while (current != null)
        {
            ++nodeCount;
            current = current.next;
        }

        if (nodeCount - n == 0)
            return head.next;

        current = head;
        for (int i = 0; i < nodeCount - n - 1; i++)
            current = current.next;

        current.next = current.next.next;

        return head;
    }
}

 

public class Solution
{
    public ListNode RemoveNthFromEnd(ListNode head, int n)
    {
        var dummy = new ListNode(0, head);
        var fast = dummy;
        var slow = dummy;

        for (int i = 0; i < n; i++)
        {
            fast = fast.next;
        }

        while (fast.next != null)
        {
            slow = slow.next;
            fast = fast.next;
        }

        slow.next = slow.next.next;
        return dummy.next;
    }
}