Find the sum of last n nodes of the given Linked List | Java implementation to find the sum of last ' n ' nodes of the Linked List ; A Linked list node ; function to insert a node at the beginning of the linked list ; allocate node ; put in the data ; link the old list to the new node ; move the head to point to the new node ; utility function to find the sum of last ' n ' nodes ; if n == 0 ; reverse the linked list ; traverse the 1 st ' n ' nodes of the reversed linked list and add them ; accumulate node ' s ▁ data ▁ to ▁ ' sum ' ; move to next node ; reverse back the linked list ; required sum ; Driver code ; create linked list 10.6 .8 .4 .12
import java . util . * ; class GFG { static class Node { int data ; Node next ; } ; static Node head ; static void push ( Node head_ref , int new_data ) { Node new_node = new Node ( ) ; new_node . data = new_data ; new_node . next = head_ref ; head_ref = new_node ; head = head_ref ; } static void reverseList ( Node head_ref ) { Node current , prev , next ; current = head_ref ; prev = null ; while ( current != null ) { next = current . next ; current . next = prev ; prev = current ; current = next ; } head_ref = prev ; head = head_ref ; } static int sumOfLastN_NodesUtil ( int n ) { if ( n <= 0 ) return 0 ; reverseList ( head ) ; int sum = 0 ; Node current = head ; while ( current != null && n -- > 0 ) { sum += current . data ; current = current . next ; } reverseList ( head ) ; return sum ; } public static void main ( String [ ] args ) { push ( head , 12 ) ; push ( head , 4 ) ; push ( head , 8 ) ; push ( head , 6 ) ; push ( head , 10 ) ; int n = 2 ; System . out . println ( " Sum ▁ of ▁ last ▁ " + n + " ▁ nodes ▁ = ▁ " + sumOfLastN_NodesUtil ( n ) ) ; } }