Remove every k-th node of the linked list
Given a singly linked list, Your task is to remove every K-th node of the linked list. Assume that K is always less than or equal to length of Linked List.
Examples :
Input : 1->2->3->4->5->6->7->8 k = 3 Output : 1->2->4->5->7->8 As 3 is the k-th node after its deletion list would be 1->2->4->5->6->7->8 And now 4 is the starting node then from it, 6 would be the k-th node. So no other kth node could be there.So, final list is: 1->2->4->5->7->8. Input: 1->2->3->4->5->6 k = 1 Output: Empty list All nodes need to be deleted
The idea is to traverse the list from the beginning and keep track of nodes visited after the last deletion. Whenever count becomes k, delete the current node and reset the count as 0.
(1) Traverse list and do following (a) Count node before deletion. (b) If (count == k) that means current node is to be deleted. (i) Delete current node i.e. do // assign address of next node of // current node to the previous node // of the current node. prev->next = ptr->next i.e. (ii) Reset count as 0, i.e., do count = 0. (c) Update prev node if count != 0 and if count is 0 that means that node is a starting point. (d) Update ptr and continue until all k-th node gets deleted.
Below is the implementation.
C++
// C++ program to delete every k-th Node of // a singly linked list. #include<bits/stdc++.h> using namespace std; /* Linked list Node */ struct Node { int data; struct Node* next; }; // To remove complete list (Needed for // case when k is 1) void freeList(Node *node) { while (node != NULL) { Node *next = node->next; delete (node); node = next; } } // Deletes every k-th node and returns head // of modified list. Node *deleteKthNode( struct Node *head, int k) { // If linked list is empty if (head == NULL) return NULL; if (k == 1) { freeList(head); return NULL; } // Initialize ptr and prev before starting // traversal. struct Node *ptr = head, *prev = NULL; // Traverse list and delete every k-th node int count = 0; while (ptr != NULL) { // increment Node count count++; // check if count is equal to k // if yes, then delete current Node if (k == count) { // put the next of current Node in // the next of previous Node delete (prev->next); prev->next = ptr->next; // set count = 0 to reach further // k-th Node count = 0; } // update prev if count is not 0 if (count != 0) prev = ptr; ptr = prev->next; } return head; } /* Function to print linked list */ void displayList( struct Node *head) { struct Node *temp = head; while (temp != NULL) { cout<<temp->data<< " " ; temp = temp->next; } } // Utility function to create a new node. struct Node *newNode( int x) { Node *temp = new Node; temp->data = x; temp->next = NULL; return temp; } /* Driver program to test count function*/ int main() { /* Start with the empty list */ struct Node* head = newNode(1); head->next = newNode(2); head->next->next = newNode(3); head->next->next->next = newNode(4); head->next->next->next->next = newNode(5); head->next->next->next->next->next = newNode(6); head->next->next->next->next->next->next = newNode(7); head->next->next->next->next->next->next->next = newNode(8); int k = 3; head = deleteKthNode(head, k); displayList(head); return 0; } |
Java
// Java program to delete every k-th Node // of a singly linked list. class GFG { /* Linked list Node */ static class Node { int data; Node next; } // To remove complete list (Needed for // case when k is 1) static Node freeList(Node node) { while (node != null ) { Node next = node.next; node = next; } return node; } // Deletes every k-th node and // returns head of modified list. static Node deleteKthNode(Node head, int k) { // If linked list is empty if (head == null ) return null ; if (k == 1 ) { head = freeList(head); return null ; } // Initialize ptr and prev before // starting traversal. Node ptr = head, prev = null ; // Traverse list and delete // every k-th node int count = 0 ; while (ptr != null ) { // increment Node count count++; // check if count is equal to k // if yes, then delete current Node if (k == count) { // put the next of current Node in // the next of previous Node prev.next = ptr.next; // set count = 0 to reach further // k-th Node count = 0 ; } // update prev if count is not 0 if (count != 0 ) prev = ptr; ptr = prev.next; } return head; } /* Function to print linked list */ static void displayList(Node head) { Node temp = head; while (temp != null ) { System.out.print(temp.data + " " ); temp = temp.next; } } // Utility function to create a new node. static Node newNode( int x) { Node temp = new Node(); temp.data = x; temp.next = null ; return temp; } // Driver Code public static void main(String args[]) { /* Start with the empty list */ Node head = newNode( 1 ); head.next = newNode( 2 ); head.next.next = newNode( 3 ); head.next.next.next = newNode( 4 ); head.next.next.next.next = newNode( 5 ); head.next.next.next.next.next = newNode( 6 ); head.next.next.next.next.next.next = newNode( 7 ); head.next.next.next.next.next.next.next = newNode( 8 ); int k = 3 ; head = deleteKthNode(head, k); displayList(head); } } // This code is contributed by Arnab Kundu |
Python3
# Python3 program to delete every k-th Node # of a singly linked list. import math # Linked list Node class Node: def __init__( self , data): self .data = data self . next = None # To remove complete list (Needed for # case when k is 1) def freeList(node): while (node ! = None ): next = node. next node = next return node # Deletes every k-th node and # returns head of modified list. def deleteKthNode(head, k): # If linked list is empty if (head = = None ): return None if (k = = 1 ): freeList(head) return None # Initialize ptr and prev before # starting traversal. ptr = head prev = None # Traverse list and delete every k-th node count = 0 while (ptr ! = None ): # increment Node count count = count + 1 # check if count is equal to k # if yes, then delete current Node if (k = = count): # put the next of current Node in # the next of previous Node # delete(prev.next) prev. next = ptr. next # set count = 0 to reach further # k-th Node count = 0 # update prev if count is not 0 if (count ! = 0 ): prev = ptr ptr = prev. next return head # Function to print linked list def displayList(head): temp = head while (temp ! = None ): print (temp.data, end = ' ' ) temp = temp. next # Utility function to create a new node. def newNode( x): temp = Node(x) temp.data = x temp. next = None return temp # Driver Code if __name__ = = '__main__' : # Start with the empty list head = newNode( 1 ) head. next = newNode( 2 ) head. next . next = newNode( 3 ) head. next . next . next = newNode( 4 ) head. next . next . next . next = newNode( 5 ) head. next . next . next . next . next = newNode( 6 ) head. next . next . next . next . next . next = newNode( 7 ) head. next . next . next . next . next . next . next = newNode( 8 ) k = 3 head = deleteKthNode(head, k) displayList(head) # This code is contributed by Srathore |
C#
// C# program to delete every k-th Node // of a singly linked list. using System; class GFG { /* Linked list Node */ public class Node { public int data; public Node next; } // To remove complete list (Needed for // case when k is 1) static Node freeList(Node node) { while (node != null ) { Node next = node.next; node = next; } return node; } // Deletes every k-th node and // returns head of modified list. static Node deleteKthNode(Node head, int k) { // If linked list is empty if (head == null ) return null ; if (k == 1) { head = freeList(head); return null ; } // Initialize ptr and prev before // starting traversal. Node ptr = head, prev = null ; // Traverse list and delete // every k-th node int count = 0; while (ptr != null ) { // increment Node count count++; // check if count is equal to k // if yes, then delete current Node if (k == count) { // put the next of current Node in // the next of previous Node prev.next = ptr.next; // set count = 0 to reach further // k-th Node count = 0; } // update prev if count is not 0 if (count != 0) prev = ptr; ptr = prev.next; } return head; } /* Function to print linked list */ static void displayList(Node head) { Node temp = head; while (temp != null ) { Console.Write(temp.data + " " ); temp = temp.next; } } // Utility function to create a new node. static Node newNode( int x) { Node temp = new Node(); temp.data = x; temp.next = null ; return temp; } // Driver Code public static void Main(String []args) { /* Start with the empty list */ Node head = newNode(1); head.next = newNode(2); head.next.next = newNode(3); head.next.next.next = newNode(4); head.next.next.next.next = newNode(5); head.next.next.next.next.next = newNode(6); head.next.next.next.next.next.next = newNode(7); head.next.next.next.next.next.next.next = newNode(8); int k = 3; head = deleteKthNode(head, k); displayList(head); } } // This code is contributed by PrinciRaj1992 |
Javascript
<script> // Javascript program to delete every k-th Node // of a singly linked list. /* Linked list Node */ class Node { constructor() { this .data = 0; this .next = null ; } } // To remove complete list (Needed for // case when k is 1) function freeList( node) { while (node != null ) { next = node.next; node = next; } return node; } // Deletes every k-th node and // returns head of modified list. function deleteKthNode( head , k) { // If linked list is empty if (head == null ) return null ; if (k == 1) { head = freeList(head); return null ; } // Initialize ptr and prev before // starting traversal. var ptr = head, prev = null ; // Traverse list and delete // every k-th node var count = 0; while (ptr != null ) { // increment Node count count++; // check if count is equal to k // if yes, then delete current Node if (k == count) { // put the next of current Node in // the next of previous Node prev.next = ptr.next; // set count = 0 to reach further // k-th Node count = 0; } // update prev if count is not 0 if (count != 0) prev = ptr; ptr = prev.next; } return head; } /* Function to print linked list */ function displayList( head) { temp = head; while (temp != null ) { document.write(temp.data + " " ); temp = temp.next; } } // Utility function to create a new node. function newNode(x) { temp = new Node(); temp.data = x; temp.next = null ; return temp; } // Driver Code /* Start with the empty list */ head = newNode(1); head.next = newNode(2); head.next.next = newNode(3); head.next.next.next = newNode(4); head.next.next.next.next = newNode(5); head.next.next.next.next.next = newNode(6); head.next.next.next.next.next.next = newNode(7); head.next.next.next.next.next.next.next = newNode(8); var k = 3; head = deleteKthNode(head, k); displayList(head); // This code contributed by umadevi9616 </script> |
Output
1 2 1
Time Complexity : O(n)
Auxiliary Space : O(1)
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