Delete N nodes after M nodes of a linked list
Given a linked list and two integers M and N. Traverse the linked list such that you retain M nodes then delete next N nodes, continue the same till end of the linked list.
Difficulty Level: Rookie
Examples:
Input: M = 2, N = 2 Linked List: 1->2->3->4->5->6->7->8 Output: Linked List: 1->2->5->6 Input: M = 3, N = 2 Linked List: 1->2->3->4->5->6->7->8->9->10 Output: Linked List: 1->2->3->6->7->8 Input: M = 1, N = 1 Linked List: 1->2->3->4->5->6->7->8->9->10 Output: Linked List: 1->3->5->7->9
The main part of the problem is to maintain proper links between nodes, make sure that all corner cases are handled. Following is C implementation of function skipMdeleteN() that skips M nodes and delete N nodes till end of list. It is assumed that M cannot be 0.
C++
// C++ program to delete N nodes// after M nodes of a linked list #include <bits/stdc++.h>using namespace std; // A linked list node class Node { public: int data; Node *next; }; /* Function to insert a node at the beginning */void push(Node ** head_ref, int new_data) { /* allocate node */ Node* new_node = new Node(); /* put in the data */ new_node->data = new_data; /* link the old list off the new node */ new_node->next = (*head_ref); /* move the head to point to the new node */ (*head_ref) = new_node; } /* Function to print linked list */void printList(Node *head) { Node *temp = head; while (temp != NULL) { cout<<temp->data<<" "; temp = temp->next; } cout<<endl; } // Function to skip M nodes and then// delete N nodes of the linked list. void skipMdeleteN(Node *head, int M, int N) { Node *curr = head, *t; int count; // The main loop that traverses // through the whole list while (curr) { // Skip M nodes for (count = 1; count < M && curr!= NULL; count++) curr = curr->next; // If we reached end of list, then return if (curr == NULL) return; // Start from next node and delete N nodes t = curr->next; for (count = 1; count<=N && t!= NULL; count++) { Node *temp = t; t = t->next; free(temp); } // Link the previous list with remaining nodes curr->next = t; // Set current pointer for next iteration curr = t; } } // Driver code int main() { /* Create following linked list 1->2->3->4->5->6->7->8->9->10 */ Node* head = NULL; int M=2, N=3; push(&head, 10); push(&head, 9); push(&head, 8); push(&head, 7); push(&head, 6); push(&head, 5); push(&head, 4); push(&head, 3); push(&head, 2); push(&head, 1); cout << "M = " << M<< " N = " << N << "\nGiven Linked list is :\n"; printList(head); skipMdeleteN(head, M, N); cout<<"\nLinked list after deletion is :\n"; printList(head); return 0; } // This code is contributed by rathbhupendra |
C
// C program to delete N nodes after M nodes of a linked list#include <stdio.h>#include <stdlib.h> // A linked list nodestruct Node{ int data; struct Node *next;}; /* Function to insert a node at the beginning */void push(struct Node ** head_ref, int new_data){ /* allocate node */ struct Node* new_node = (struct Node*) malloc(sizeof(struct Node)); /* put in the data */ new_node->data = new_data; /* link the old list off the new node */ new_node->next = (*head_ref); /* move the head to point to the new node */ (*head_ref) = new_node;} /* Function to print linked list */void printList(struct Node *head){ struct Node *temp = head; while (temp != NULL) { printf("%d ", temp->data); temp = temp->next; } printf("\n");} // Function to skip M nodes and then delete N nodes of the linked list.void skipMdeleteN(struct Node *head, int M, int N){ struct Node *curr = head, *t; int count; // The main loop that traverses through the whole list while (curr) { // Skip M nodes for (count = 1; count<M && curr!= NULL; count++) curr = curr->next; // If we reached end of list, then return if (curr == NULL) return; // Start from 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); } curr->next = t; // Link the previous list with remaining nodes // Set current pointer for next iteration curr = t; }} // Driver program to test above functionsint main(){ /* Create following linked list 1->2->3->4->5->6->7->8->9->10 */ struct Node* head = NULL; int M=2, N=3; push(&head, 10); push(&head, 9); push(&head, 8); push(&head, 7); push(&head, 6); push(&head, 5); push(&head, 4); push(&head, 3); push(&head, 2); push(&head, 1); printf("M = %d, N = %d \nGiven Linked list is :\n", M, N); printList(head); skipMdeleteN(head, M, N); printf("\nLinked list after deletion is :\n"); printList(head); return 0;} |
Java
// Java program to delete N nodes // after M nodes of a linked list import java.util.*; class GFG{ // A linked list node static class Node { int data; Node next; }; /* Function to insert a node at the beginning */static Node push( Node head_ref, int new_data) { /* allocate node */ Node new_node = new Node(); /* put in the data */ new_node.data = new_data; /* link the old list off the new node */ new_node.next = (head_ref); /* move the head to point to the new node */ (head_ref) = new_node; return head_ref;} /* Function to print linked list */static void printList( Node head) { Node temp = head; while (temp != null) { System.out.printf("%d ", temp.data); temp = temp.next; } System.out.printf("\n"); } // Function to skip M nodes and then// delete N nodes of the linked list. static void skipMdeleteN( Node head, int M, int N) { Node curr = head, t; int count; // The main loop that traverses // through the whole list while (curr!=null) { // Skip M nodes for (count = 1; count < M && curr != null; count++) curr = curr.next; // If we reached end of list, then return if (curr == null) return; // Start from next node and delete N nodes t = curr.next; for (count = 1; count <= N && t != null; count++) { Node temp = t; t = t.next; } // Link the previous list with remaining nodes curr.next = t; // Set current pointer for next iteration curr = t; } } // Driver code public static void main(String args[]){ /* Create following linked list 1.2.3.4.5.6.7.8.9.10 */ Node head = null; int M=2, N=3; head=push(head, 10); head=push(head, 9); head=push(head, 8); head=push(head, 7); head=push(head, 6); head=push(head, 5); head=push(head, 4); head=push(head, 3); head=push(head, 2); head=push(head, 1); System.out.printf("M = %d, N = %d \nGiven" + "Linked list is :\n", M, N); printList(head); skipMdeleteN(head, M, N); System.out.printf("\nLinked list after deletion is :\n"); printList(head); } } // This code is contributed by Arnab Kundu |
Python
# Python program to delete M nodes after N nodes # Node class class Node: # Constructor to initialize the node object def __init__(self, data): self.data = data self.next = None class LinkedList: # Function to initialize head def __init__(self): self.head = None # Function to insert a new node at the beginning def push(self, new_data): new_node = Node(new_data) new_node.next = self.head self.head = new_node # Utility function to prit the linked LinkedList def printList(self): temp = self.head while(temp): print temp.data, temp = temp.next def skipMdeleteN(self, M, N): curr = self.head # The main loop that traverses through the # whole list while(curr): # Skip M nodes for count in range(1, M): if curr is None: return curr = curr.next if curr is None : return # Start from next node and delete N nodes t = curr.next for count in range(1, N+1): if t is None: break t = t.next # Link the previous list with reamining nodes curr.next = t # Set Current pointer for next iteration curr = t # Driver program to test above function # Create following linked list# 1->2->3->4->5->6->7->8->9->10llist = LinkedList()M = 2 N = 3llist.push(10)llist.push(9)llist.push(8)llist.push(7)llist.push(6)llist.push(5)llist.push(4)llist.push(3)llist.push(2)llist.push(1) print "M = %d, N = %d\nGiven Linked List is:" %(M, N)llist.printList()print llist.skipMdeleteN(M, N) print "\nLinked list after deletion is"llist.printList() # This code is contributed by Nikhil Kumar Singh(nickzuck_007) |
C#
// C# program to delete N nodes // after M nodes of a linked list using System; class GFG { // A linked list node public class Node { public int data; public Node next; }; /* Function to insert a node at the beginning */static Node push( Node head_ref, int new_data) { /* allocate node */ Node new_node = new Node(); /* put in the data */ new_node.data = new_data; /* link the old list off the new node */ new_node.next = (head_ref); /* move the head to point to the new node */ (head_ref) = new_node; return head_ref; } /* Function to print linked list */static void printList( Node head) { Node temp = head; while (temp != null) { Console.Write("{0} ", temp.data); temp = temp.next; } Console.Write("\n"); } // Function to skip M nodes and then // delete N nodes of the linked list. static void skipMdeleteN( Node head, int M, int N) { Node curr = head, t; int count; // The main loop that traverses // through the whole list while (curr!=null) { // Skip M nodes for (count = 1; count < M && curr != null; count++) curr = curr.next; // If we reached end of list, then return if (curr == null) return; // Start from next node and delete N nodes t = curr.next; for (count = 1; count <= N && t != null; count++) { Node temp = t; t = t.next; } // Link the previous list with remaining nodes curr.next = t; // Set current pointer for next iteration curr = t; } } // Driver code public static void Main(String []args) { /* Create following linked list 1.2.3.4.5.6.7.8.9.10 */ Node head = null; int M=2, N=3; head=push(head, 10); head=push(head, 9); head=push(head, 8); head=push(head, 7); head=push(head, 6); head=push(head, 5); head=push(head, 4); head=push(head, 3); head=push(head, 2); head=push(head, 1); Console.Write("M = {0}, N = {1} \nGiven" + "Linked list is :\n", M, N); printList(head); skipMdeleteN(head, M, N); Console.Write("\nLinked list after deletion is :\n"); printList(head); } } // This code contributed by Rajput-Ji |
Output:
M = 2, N = 3 Given Linked list is : 1 2 3 4 5 6 7 8 9 10 Linked list after deletion is : 1 2 6 7
Time Complexity: O(n) where n is number of nodes in linked list.
This article is contributed by Chandra Prakash. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
