Given head of a linked list of integers and an integer k, your task is to modify the linked list as follows:
- Consider nodes in groups of size k. In every group, replace value of first node with group sum.
- Also, delete the elements of group except the first node.
- During traversal, if the remaining nodes in linked list are less than k then also do the above considering remaining nodes.
Examples:
Input: N = 6, K = 2
1->2->3->4->5->6
Output: 3 7 11
We have denoted grouping of k elements by (). The elements inside () are summed.
1 -> 2 -> 3 -> 4 -> 5 -> 6 -> null
(1 -> 2) -> 3 -> 4 -> 5 -> 6 -> null
(3) -> 3 -> 4 -> 5 -> 6 -> null
3 -> (3 -> 4) -> 5 -> 6 -> null
3 -> (7) -> 5 -> 6 -> null
3 -> 7 -> (5 -> 6) -> null
3 -> 7 -> (11) -> null
3 -> 7 -> 11 -> null
Approach:
Insert the given nodes in the Linked list. The approach of insertion has been discussed in this post. Once the nodes are inserted, iterate from the beginning of the list. Mark the first node as temp node. Iterate for the next k-1 nodes and sum up the nodes in sum variable. If the number of nodes is less than K, then replace the temp node's data with sum and point temp to NULL.
If there is a group with K nodes, replace the temp's data with sum and move temp to the node which is just after K nodes. Continue the above operation till temp points to NULL. Once temp reaches the end, it means all groups of size K has been traversed and the node has been replaced with the sum of nodes of size K. Once the operation of replacements have been done, the linked list thus formed can be printed. The method of printing the linked list has been discussed in this post.
Below is the implementation of the above approach:
// C++ program for
// SP - K Sum
#include <iostream>
using namespace std;
// structure for linked list
struct Node {
long long data;
Node* next;
};
// allocated new node
Node* newNode(int key)
{
Node* temp = new Node;
temp->data = key;
temp->next = NULL;
return temp;
}
// function to insert node in a Linked List
Node* insertNode(Node* head, int key)
{
if (head == NULL)
head = newNode(key);
else
head->next = insertNode(head->next, key);
return head;
}
// traverse the node
// to print it
void print(Node* head)
{
// traverse the linked list
while (head) {
cout << head->data << " ";
head = head->next;
}
cout << endl;
}
// function to perform the following operation
void KSum(Node* head, int k)
{
// initially pointing to start
Node* temp = head;
// iterate till end
while (temp) {
// dummy variable to store k
long long count = k;
// summation of nodes
long long sum = 0;
// currently at node from
// which iteration is done
Node* curr = temp;
// till k nodes are visited and
// last node is not visited
while (count-- && curr) {
// add to sum the node data
sum = sum + curr->data;
// move to the next node
curr = curr->next;
}
// change pointer's data of temp to sum
temp->data = sum;
// move temp to next pointer
temp->next = curr;
// move temp to the next pointer
temp = temp->next;
}
}
// Driver Code
int main()
{
Node* head = NULL;
// inserts nodes in the linked list
head = insertNode(head, 1);
head = insertNode(head, 2);
head = insertNode(head, 3);
head = insertNode(head, 4);
head = insertNode(head, 5);
head = insertNode(head, 6);
int k = 2;
// Function call to perform the
// given operations
KSum(head, k);
// print the linked list
print(head);
return 0;
}
// Java program for
// SP - K Sum
import java.io.*;
import java.util.*;
// structure for linked list
class Node
{
int data;
Node next;
Node(int key)
{
data = key;
next = null;
}
}
class GFG
{
// allocated new node
static Node head;
// function to insert node
// in a Linked List
public static Node insertNode(Node head, int key)
{
if (head == null)
head = new Node(key);
else
head.next = insertNode(head.next, key);
return head;
}
// traverse the node
// to print it
public static void print(Node head)
{
// traverse the linked list
while (head != null)
{
System.out.print(head.data + " ");
head = head.next;
}
System.out.println();
}
// function to perform
// the following operation
public static void KSum(Node head, int k)
{
// initially pointing
// to start
Node temp = head;
// iterate till end
while (temp != null)
{
// dummy variable
// to store k
int count = k;
// summation of nodes
int sum = 0;
// currently at node from
// which iteration is done
Node curr = temp;
// till k nodes are visited and
// last node is not visited
while (count > 0 && curr != null)
{
// add to sum the node data
sum = sum + curr.data;
// move to the next node
curr = curr.next;
count--;
}
// change pointer's data
// of temp to sum
temp.data = sum;
// move temp to
// next pointer
temp.next = curr;
// move temp to
// the next pointer
temp = temp.next;
}
//return temp;
}
// Driver Code
public static void main(String args[])
{
head = null;
// inserts nodes in
// the linked list
head = insertNode(head, 1);
head = insertNode(head, 2);
head = insertNode(head, 3);
head = insertNode(head, 4);
head = insertNode(head, 5);
head = insertNode(head, 6);
int k = 2;
// Function call to perform
// the given operations
KSum(head, k);
// print the linked list
print(head);
}
}
# Python program for
# SP - K Sum
# structure for linked list
class Node:
def __init__(self, key):
self.data = key
self.next = None
# function to insert node in a Linked List
def insertNode(head: Node, key: int) -> Node:
if head is None:
head = Node(key)
else:
head.next = insertNode(head.next, key)
return head
# traverse the node
# to print it
def Print(head: Node):
# traverse the linked list
while head:
print(head.data, end = " ")
head = head.next
print()
# function to perform the following operation
def KSum(head: Node, k: int):
# initially pointing to start
temp = head
# iterate till end
while temp:
# dummy variable to store k
count = k
# summation of nodes
sum = 0
# currently at node from
# which iteration is done
curr = temp
# till k nodes are visited and
# last node is not visited
while count and curr:
# add to sum the node data
sum = sum + curr.data
# move to the next node
curr = curr.next
count -= 1
# change pointer's data of temp to sum
temp.data = sum
# move temp to next pointer
temp.next = curr
# move temp to the next pointer
temp = temp.next
# Driver Code
if __name__ == "__main__":
head = None
# inserts nodes in the linked list
head = insertNode(head, 1)
head = insertNode(head, 2)
head = insertNode(head, 3)
head = insertNode(head, 4)
head = insertNode(head, 5)
head = insertNode(head, 6)
k = 2
# Function call to perform the
# given operations
KSum(head, k)
# print the linked list
Print(head)
# This code is contributed by
# sanjeev2552
// C# program for SP - K Sum
using System;
// structure for linked list
public class Node
{
public int data;
public Node next;
public Node(int key)
{
data = key;
next = null;
}
}
public class GFG
{
// allocated new node
static Node head;
// function to insert node
// in a Linked List
public static Node insertNode(Node head, int key)
{
if (head == null)
head = new Node(key);
else
head.next = insertNode(head.next, key);
return head;
}
// traverse the node
// to print it
public static void print(Node head)
{
// traverse the linked list
while (head != null)
{
Console.Write(head.data + " ");
head = head.next;
}
Console.WriteLine();
}
// function to perform
// the following operation
public static void KSum(Node head, int k)
{
// initially pointing
// to start
Node temp = head;
// iterate till end
while (temp != null)
{
// dummy variable
// to store k
int count = k;
// summation of nodes
int sum = 0;
// currently at node from
// which iteration is done
Node curr = temp;
// till k nodes are visited and
// last node is not visited
while (count > 0 && curr != null)
{
// add to sum the node data
sum = sum + curr.data;
// move to the next node
curr = curr.next;
count--;
}
// change pointer's data
// of temp to sum
temp.data = sum;
// move temp to
// next pointer
temp.next = curr;
// move temp to
// the next pointer
temp = temp.next;
}
// return temp;
}
// Driver Code
public static void Main()
{
head = null;
// inserts nodes in
// the linked list
head = insertNode(head, 1);
head = insertNode(head, 2);
head = insertNode(head, 3);
head = insertNode(head, 4);
head = insertNode(head, 5);
head = insertNode(head, 6);
int k = 2;
// Function call to perform
// the given operations
KSum(head, k);
// print the linked list
print(head);
}
}
/* This code contributed by PrinciRaj1992 */
<script>
// JavaScript program for SP - K Sum
// structure for linked list
class Node
{
constructor(key)
{
this.data = key;
this.next = null;
}
}
// allocated new node
var head = null;
// function to insert node
// in a Linked List
function insertNode(head, key)
{
if (head == null) head = new Node(key);
else head.next = insertNode(head.next, key);
return head;
}
// traverse the node
// to print it
function print(head)
{
// traverse the linked list
while (head != null)
{
document.write(head.data + " ");
head = head.next;
}
document.write("<br>");
}
// function to perform
// the following operation
function KSum(head, k)
{
// initially pointing
// to start
var temp = head;
// iterate till end
while (temp != null)
{
// dummy variable
// to store k
var count = k;
// summation of nodes
var sum = 0;
// currently at node from
// which iteration is done
var curr = temp;
// till k nodes are visited and
// last node is not visited
while (count > 0 && curr != null)
{
// add to sum the node data
sum = sum + curr.data;
// move to the next node
curr = curr.next;
count--;
}
// change pointer's data
// of temp to sum
temp.data = sum;
// move temp to
// next pointer
temp.next = curr;
// move temp to
// the next pointer
temp = temp.next;
}
// return temp;
}
// Driver Code
head = null;
// inserts nodes in
// the linked list
head = insertNode(head, 1);
head = insertNode(head, 2);
head = insertNode(head, 3);
head = insertNode(head, 4);
head = insertNode(head, 5);
head = insertNode(head, 6);
var k = 2;
// Function call to perform
// the given operations
KSum(head, k);
// print the linked list
print(head);
// This code is contributed by rdtank.
</script>
Output
3 7 11