Add K Nodes

Posted: 29 Sep, 2020
Difficulty: Moderate

PROBLEM STATEMENT

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You are given a Singly Linked List of integers and an integer 'K'.

Your task is to modify the linked list by inserting a new node after every 'K' node in the linked list with the node value being equal to the sum of the previous 'K' nodes.

Note :
If you reach a situation when the number of nodes remaining in the linked list is less than 'K' but greater than zero, just insert a node with the value equal to the sum of the remaining nodes.
Input Format
The first line of the input contains the elements of the singly linked list separated by a single space and terminated by -1. Hence, -1 would never be a list element.

The second line contains a single integer 'K'.
Output Format:
Print the modified linked list. 

The elements of the modified list should be single-space separated, terminated by -1.
Note:
You are not required to print the output, it has already been taken care of. Just implement the function.
Constraints:
0 <= L <= 5 * 10^5
-10^3 <= data <= 10^3 and data != -1
1 <= K <= 10^6

where 'L' is the number of nodes in the linked list and 'data' is the value of elements present in the given linked list.

Time Limit: 1 sec
Approach 1
  • We will iterate through the linked list and store the sum of the nodes in a variable 'CURR_SUM' (initialized as zero) and keep a check of the number of nodes traversed since the last insertion with a variable 'NODES_TRAVERSED' (also, initialized as zero).
  • As we traverse the list, we add the value to the 'CURR_SUM' and increment the value of 'NODES_TRAVERSED'.
  • When the value of 'NODES_TRAVERSED'becomes equal to ‘K’, we insert a node after the current node with its value being equal to 'CURR_SUM'.
  • Now, we move to the next node in the list, resetting the value of 'CURR_SUM' and 'NODES_TRAVERSED'.
  • We follow the above steps till we reach the last node of the linked list.
  • After considering the last node, if the value of ‘NODES_TRAVERSED’ is greater than 0, we insert a node at the end of the list with its value equal to the value of 'CURR_SUM'.
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