Count triplets in a sorted doubly linked list whose product is equal to a given value x | Java implementation to count triplets in a sorted doubly linked list whose product is equal to a given value ' x ' ; structure of node of doubly linked list ; function to count pairs whose product equal to given ' value ' ; The loop terminates when either of two pointers become null , or they cross each other ( second . next == first ) , or they become same ( first == second ) ; pair found ; increment count ; move first in forward direction ; move second in backward direction ; if product is greater than ' value ' move second in backward direction ; else move first in forward direction ; required count of pairs ; function to count triplets in a sorted doubly linked list whose product is equal to a given value ' x ' ; if list is empty ; get pointer to the last node of the doubly linked list ; traversing the doubly linked list ; for each current node ; count pairs with product ( x / current . data ) in the range first to last and add it to the ' count ' of triplets ; required count of triplets ; A utility function to insert a new node at the beginning of doubly linked list ; allocate node ; put in the data ; Driver code ; start with an empty doubly linked list ; insert values in sorted order
import java . util . * ; class GFG { static class Node { int data ; Node next , prev ; } ; static int countPairs ( Node first , Node second , int value ) { int count = 0 ; while ( first != null && second != null && first != second && second . next != first ) { if ( ( first . data * second . data ) == value ) { count ++ ; first = first . next ; second = second . prev ; } else if ( ( first . data * second . data ) > value ) second = second . prev ; else first = first . next ; } return count ; } static int countTriplets ( Node head , int x ) { if ( head == null ) return 0 ; Node current , first , last ; int count = 0 ; last = head ; while ( last . next != null ) last = last . next ; for ( current = head ; current != null ; current = current . next ) { first = current . next ; count += countPairs ( first , last , x / current . data ) ; } return count ; } static Node insert ( Node head , int data ) { Node temp = new Node ( ) ; temp . data = data ; temp . next = temp . prev = null ; if ( ( head ) == null ) ( head ) = temp ; else { temp . next = head ; ( head ) . prev = temp ; ( head ) = temp ; } return head ; } public static void main ( String args [ ] ) { Node head = null ; head = insert ( head , 9 ) ; head = insert ( head , 8 ) ; head = insert ( head , 6 ) ; head = insert ( head , 5 ) ; head = insert ( head , 4 ) ; head = insert ( head , 2 ) ; head = insert ( head , 1 ) ; int x = 8 ; System . out . println ( " Count ▁ = ▁ " + countTriplets ( head , x ) ) ; } }