Delete N nodes after M nodes of a linked list
Last Updated :
11 Dec, 2024
Given a linked list and two integers m and n, the task is to traverse the linked list such that you skip m nodes, then delete the next n nodes, and continue the same till end of the linked list.
Note: m cannot be 0.
Example:
Input: Linked List: 9->1->3->5->9->4->10->1, n = 1, m = 2
Output: 9->1->5->9->10->1
Explanation: Deleting 1 node after skipping 2 nodes each time, we have list as 9-> 1-> 5-> 9-> 10-> 1.
Input: Linked List: 1->2->3->4->5->6, n = 1, m = 6
Output: 1->2->3->4->5->6
Explanation: After skipping 6 nodes for the first time , we will reach of end of the linked list, so, we will get the given linked list itself.
The idea is to go through a linked list and, for every set of nodes, keep the first m nodes and delete the next n nodes, and then repeat this process until the end of the list.
Step-by-step approach:
- Start with a pointer at the first node (the head) of the linked list.
- Move this pointer forward m times, so it skips over m nodes.
- After skipping m nodes, the next n nodes should be deleted.
- To do this, we disconnect these n nodes from the list and free their memory.
- After deleting the n nodes, repeat the process starting from the next node. Skip the next m nodes and delete the following n nodes.
- This process will stops when we reach to end of the list, either because there are fewer than m nodes left to skip or there are no nodes left to delete.
Below is the implementation of the above approach:
C++
// C++ program to delete n nodes
// after m nodes of a linked list
#include <bits/stdc++.h>
using namespace std;
class Node {
public:
int data;
Node *next;
Node(int x){
data = x;
next = nullptr;
}
};
// Function to skip m nodes and then
// delete n nodes of the linked list.
Node* skipMdeleteN(Node *head, int m, int n) {
Node *curr = head, *t;
// The main loop that traverses
// through the whole list
while (curr != nullptr) {
// Skip m nodes
for (int i = 1; i < m && curr!= nullptr; i++)
curr = curr->next;
// If we reached end of list, then return
if (curr == nullptr)
return head;
// Start from next node and delete n nodes
t = curr->next;
for (int i = 1; i <= n && t!= nullptr; i++) {
Node *temp = t;
t = t->next;
delete(temp);
}
// Link the previous list with
// remaining nodes
curr->next = t;
// Set current pointer for next iteration
curr = t;
}
return head;
}
void printList(Node *head) {
Node *curr = head;
while (curr != nullptr) {
cout<<curr->data<<" ";
curr = curr->next;
}
cout<<endl;
}
int main() {
// Create following linked list:
// 1->2->3->4->5->6
Node* head = new Node(1);
head->next = new Node(2);
head->next->next = new Node(3);
head->next->next->next = new Node(4);
head->next->next->next->next = new Node(5);
head->next->next->next->next->next = new Node(6);
int m = 2, n = 2;
head = skipMdeleteN(head, m, n);
printList(head);
return 0;
}
// C program to delete n nodes after
// m nodes of a linked list
#include <stdio.h>
#include <stdlib.h>
struct Node
{
int data;
struct Node *next;
};
// Function to skip m nodes and then delete n nodes of the linked list
struct Node *skipMdeleteN(struct Node *head, int m, int n){
struct Node *curr = head; // Current node pointer
struct Node *t; // Temporary node pointer
int count; // Counter variable
// Traverse through the entire linked list
while (curr != NULL){
// Skip m nodes
for (count = 1; count < m && curr != NULL; count++)
curr = curr->next;
// If end of the list is reached, return the head
if (curr == NULL)
return head;
// Start from the next node and delete n nodes
t = curr->next;
for (count = 1; count <= n && t != NULL; count++){
struct Node *temp = t;
t = t->next;
free(temp);
}
// Link the current node to the remaining list
curr->next = t;
// Move the current pointer to the next node
curr = t;
}
return head;
}
void printList(struct Node *head){
struct Node *curr = head;
while (curr != NULL){
printf("%d ", curr->data);
curr = curr->next;
}
printf("\n");
}
struct Node *createNode(int data){
struct Node *temp = (struct Node *)malloc(sizeof(struct Node));
temp->data = data;
temp->next = NULL;
return temp;
}
int main(){
// Create the following linked list: 1->2->3->4->5->6
struct Node *head = createNode(1);
head->next = createNode(2);
head->next->next = createNode(3);
head->next->next->next = createNode(4);
head->next->next->next->next = createNode(5);
head->next->next->next->next->next = createNode(6);
int m = 2, n = 2;
head = skipMdeleteN(head, m, n);
printList(head);
return 0;
}
// Java program to delete n nodes
// after m nodes of a linked list
class Node {
int data;
Node next;
Node(int data)
{
this.data = data;
this.next = null;
}
}
class GfG {
// Function to skip m nodes and then delete n nodes
// of the linked list
static Node skipMdeleteN(Node head, int m, int n)
{
Node curr = head; // Current node pointer
Node t; // Temporary node pointer
int count; // Counter variable
// Traverse through the entire linked list
while (curr != null) {
// Skip m nodes
for (count = 1; count < m && curr != null;
count++)
curr = curr.next;
// If end of the list is reached, return the
// head
if (curr == null)
return head;
// Start from the next node and delete n nodes
t = curr.next;
for (count = 1; count <= n && t != null;
count++) {
Node temp = t;
t = t.next;
// Dereference the node for garbage
// collection
temp = null;
}
// Link the current node to the remaining list
curr.next = t;
// Move the current pointer to the next node
curr = t;
}
return head;
}
static void printList(Node head)
{
Node curr = head;
while (curr != null) {
System.out.print(curr.data + " ");
curr = curr.next;
}
System.out.println();
}
public static void main(String[] args)
{
// Create the following linked list:
// 1->2->3->4->5->6
Node head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next = new Node(5);
head.next.next.next.next.next = new Node(6);
int m = 2, n = 2;
head = skipMdeleteN(head, m, n);
printList(head);
}
}
# Python program to delete n nodes
# after m nodes of a linked list
class Node:
def __init__(self, data):
self.data = data
self.next = None
# Function to skip m nodes and then delete n nodes
# of the linked list
def skipMdeleteN(head, m, n):
curr = head # Current node pointer
count = 0 # Counter variable
# Traverse through the entire linked list
while curr:
# Skip m nodes
for count in range(1, m):
if curr is None:
return head
curr = curr.next
# If end of the list is reached, return the head
if curr is None:
return head
# Start from the next node and delete n nodes
t = curr.next
for count in range(1, n + 1):
if t is None:
break
temp = t
t = t.next
del temp # Delete the node
# Link the current node to the remaining list
curr.next = t
# Move the current pointer to the next node
curr = t
return head
def printList(head):
curr = head
while curr:
print(curr.data, end=" ")
curr = curr.next
print()
if __name__ == "__main__":
# Create the following linked list: 1->2->3->4->5->6
head = Node(1)
head.next = Node(2)
head.next.next = Node(3)
head.next.next.next = Node(4)
head.next.next.next.next = Node(5)
head.next.next.next.next.next = Node(6)
m = 2
n = 2
head = skipMdeleteN(head, m, n)
printList(head)
using System;
class Node {
public int data;
public Node next;
public Node(int data)
{
this.data = data;
this.next = null;
}
}
class GfG {
// Function to skip m nodes and then delete n nodes of
// the linked list
public static Node skipMdeleteN(Node head, int m, int n)
{
Node curr = head; // Current node pointer
Node t; // Temporary node pointer
int count; // Counter variable
// Traverse through the entire linked list
while (curr != null) {
// Skip m nodes
for (count = 1; count < m && curr != null;
count++)
curr = curr.next;
// If end of the list is reached, return the
// head
if (curr == null)
return head;
// Start from the next node and delete n nodes
t = curr.next;
for (count = 1; count <= n && t != null;
count++) {
t = t.next; // Move to the next node
}
// Link the current node to the remaining list
curr.next = t;
// Move the current pointer to the next node
curr = t;
}
return head;
}
static void printList(Node head)
{
Node curr = head;
while (curr != null) {
Console.Write(curr.data + " ");
curr = curr.next;
}
Console.WriteLine();
}
static void Main()
{
// Create the following linked list:
// 1->2->3->4->5->6
Node head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next = new Node(5);
head.next.next.next.next.next = new Node(6);
int m = 2, n = 2;
head = skipMdeleteN(head, m, n);
printList(head);
}
}
// Javascript program to delete n nodes
// after m nodes of a linked list
class Node {
constructor(data)
{
this.data = data;
this.next = null;
}
}
// Function to skip m nodes and then delete n nodes of the
// linked list
function skipMdeleteN(head, m, n)
{
let curr = head; // Current node pointer
let count = 0; // Counter variable
// Traverse through the entire linked list
while (curr !== null) {
// Skip m nodes
for (count = 1; count < m && curr !== null; count++)
curr = curr.next;
// If end of the list is reached, return the head
if (curr === null)
return head;
// Start from the next node and delete n nodes
let t = curr.next;
for (count = 1; count <= n && t !== null; count++) {
let temp = t;
t = t.next;
// Dereference the node
temp = null;
}
// Link the current node to the remaining list
curr.next = t;
// Move the current pointer to the next node
curr = t;
}
return head;
}
function printList(head)
{
let curr = head;
while (curr !== null) {
process.stdout.write(curr.data + " ");
curr = curr.next;
}
console.log();
}
// Create the following linked list: 1->2->3->4->5->6
let head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next = new Node(5);
head.next.next.next.next.next = new Node(6);
let m = 2, n = 2;
// Perform the skip and delete operation
head = skipMdeleteN(head, m, n);
// Print the modified linked list
printList(head);
Time Complexity: O(n), where n is the total number of nodes in the linked list. This is because the algorithm processes each node exactly once, either by skipping it or by deleting it.
Auxiliary Space: O(1)
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