In this post, we are going to solve the 19. Remove Nth Node From End of List problem of Leetcode. This problem 19. Remove Nth Node From End of List is a Leetcode medium level problem. Let’s see the code, 19. Remove Nth Node From End of List – Leetcode Solution.

Problem

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

Example 1 :

Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]

Example 2 :

Input: head = [1], n = 1
Output: []

Example 3 :

Input: head = [1,2], n = 1
Output: [1]

Constraints

• The number of nodes in the list is sz.
• 1 <= sz <= 30
• 0 <= Node.val <= 100
• 1 <= n <= sz

Now, let’s see the code of 19. Remove Nth Node From End of List – Leetcode Solution.

Remove Nth Node From End of List – Leetcode Solution

19. Remove Nth Node From End of List – Solution in Java

/**
 * 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 slow = head;
        ListNode fast = head;
        while(n-- > 0) fast = fast.next;
        if(fast == null){
            ListNode rn = head;
            head = head.next;
            rn = null;
            return head;
        }
        while(fast.next != null){
            slow = slow.next;
            fast = fast.next;
        }
        
        ListNode rn = slow.next;
        slow.next = rn.next;
        rn = null;
        return head;
        
    }
}

19. Remove Nth Node From End of List – Solution in C++

ListNode *removeNthFromEnd(ListNode *head, int n) 
{
    if (!head)
        return nullptr;

    ListNode new_head(-1);
    new_head.next = head;

    ListNode *slow = &new_head, *fast = &new_head;

    for (int i = 0; i < n; i++)
        fast = fast->next;

    while (fast->next) 
    {
        fast = fast->next;
        slow = slow->next;
    }

    ListNode *to_de_deleted = slow->next;
    slow->next = slow->next->next;
    
    delete to_be_deleted;

    return new_head.next;
}

19. Remove Nth Node From End of List – Solution in Python

def removeNthFromEnd(self, head, n):
    fast = slow = dummy = ListNode(0)
    dummy.next = head
    for _ in xrange(n):
        fast = fast.next
    while fast and fast.next:
        fast = fast.next
        slow = slow.next
    slow.next = slow.next.next
    return dummy.next

Note: This problem 19. Remove Nth Node From End of List is generated by Leetcode but the solution is provided by CodingBroz. This tutorial is only for Educational and Learning purpose.