Remove Nth node from the back of the LL
IntuitThe problem
Given the head of a singly linked list and an integer n. Remove the nth node from the back of the linked List and return the head of the modified list. The value of n will always be less than or equal to the number of nodes in the linked list.
Input: linkedList = 1 -> 2 -> 3 -> 4 -> 5, n = 2 Output: 1 -> 2 -> 3 -> 5 Explanation: The 2nd node from the back was the node with value 4.
Input: linkedList = 5 -> 4 -> 3 -> 2 -> 1, n = 5 Output: 4 -> 3 -> 2 -> 1 Explanation: The 5th node from the back is the first node.
Input: linkedList = 9 -> 8 -> 7, n = 1
- 1 <= number of nodes in the Linked List <= 105
- 0 <= ListNode.val <= 104
- 1 <= n <= number of nodes in the Linked List.
cpp
/*
Definition of singly linked list:
struct ListNode
{
int val;
ListNode *next;
ListNode()
{
val = 0;
next = NULL;
}
ListNode(int data1)
{
val = data1;
next = NULL;
}
ListNode(int data1, ListNode *next1)
{
val = data1;
next = next1;
}
};
*/
class Solution {
public:
ListNode* removeNthFromEnd(ListNode* head, int n) {
}
};java
/*Definition for Singly Linked List
class ListNode {
int val;
ListNode next;
ListNode() {
val = 0;
next = null;
}
ListNode(int data1) {
val = data1;
next = null;
}
ListNode(int data1, ListNode next1) {
val = data1;
next = next1;
}
}
*/
class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
}
}python
# Definition for Singly Linked List
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution:
def removeNthFromEnd(self, head, n):javascript
/*Definition for Singly Linked List
class ListNode {
constructor(val = 0, next = null) {
this.val = val;
this.next = next;
}
}
*/
class Solution {
removeNthFromEnd(head, n) {
}
}csharp
/*
Definition for Singly Linked List
public class ListNode {
public int val;
public ListNode next;
public ListNode(int val=0, ListNode next=null) {
this.val = val;
this.next = next;
}
}
*/
public class Solution {
public ListNode RemoveNthFromEnd(ListNode head, int n) {
}
}go
func removeNthFromEnd(head *ListNode, n int) *ListNode {
}Stuck? Show a way to structure it+
- 01Add a dummy before head
- 02Advance fast by n+1 nodes with input validation
- 03Move both pointers until fast is null
- 04Bypass slow.next and return dummy.next
Reference answer
Then expect these follow-ups
How would you do this with a length pass?
Tests: follow-up reasoning
Why does the dummy simplify head deletion?
Tests: correctness reasoning
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