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# Count pairs from two linked lists whose product is equal to a given value

• Last Updated : 28 May, 2021

Given two linked lists(can be sorted or unsorted) of size n1 and n2 of distinct elements. Given a value X. The problem is to count all pairs from both lists whose product is equal to the given value x.
Note:The pair must have an element from each linked list.
Examples

```Input : list1 = 3->1->5->7
list2 = 8->2->5->3
X = 10
Output : 1
The pair is: (5, 2)

Input : list1 = 4->3->5->7->11->2->1
list2 = 2->3->4->5->6->8-12
X = 9
Output : 1
The pair is: (3, 3)```

A simple approach is using two loops pick elements from both the linked lists and check whether the product of the pair is equal to the given value X or not. Count all such pairs and print the result.
Below is the implementation of the above approach:

## C++

 `// C++ program to count all pairs from both the``// linked lists whose product is equal to``// a given value` `#include ``using` `namespace` `std;` `/* A Linked list node */``struct` `Node {``    ``int` `data;``    ``struct` `Node* next;``};` `// function to insert a node at the``// beginning of the linked list``void` `push(``struct` `Node** head_ref, ``int` `new_data)``{``    ``/* allocate node */``    ``struct` `Node* new_node = (``struct` `Node*)``malloc``(``sizeof``(``struct` `Node));` `    ``/* put in the data */``    ``new_node->data = new_data;` `    ``/* link the old list to the new node */``    ``new_node->next = (*head_ref);` `    ``/* move the head to point to the new node */``    ``(*head_ref) = new_node;``}` `// Function to count all pairs from both the linked lists``// whose product is equal to a given value``int` `countPairs(``struct` `Node* head1, ``struct` `Node* head2, ``int` `x)``{``    ``int` `count = 0;` `    ``struct` `Node *p1, *p2;` `    ``// Traverse the 1st linked list``    ``for` `(p1 = head1; p1 != NULL; p1 = p1->next) {``        ``// for each node of 1st list``        ``// Traverse the 2nd list``        ``for` `(p2 = head2; p2 != NULL; p2 = p2->next) {``            ``// if sum of pair is equal to 'x'``            ``// increment count``            ``if` `((p1->data * p2->data) == x)``                ``count++;``        ``}``    ``}` `    ``// required count of pairs``    ``return` `count;``}` `// Driver Code``int` `main()``{``    ``struct` `Node* head1 = NULL;``    ``struct` `Node* head2 = NULL;` `    ``// create linked list1 3->1->5->7``    ``push(&head1, 7);``    ``push(&head1, 5);``    ``push(&head1, 1);``    ``push(&head1, 3);` `    ``// create linked list2 8->2->5->3``    ``push(&head2, 3);``    ``push(&head2, 5);``    ``push(&head2, 2);``    ``push(&head2, 8);` `    ``int` `x = 10;` `    ``cout << ``"Count = "` `<< countPairs(head1, head2, x);` `    ``return` `0;``}`

## Java

 `// Java program to count all pairs from both the``// linked lists whose product is equal to``// a given value` `class` `GFG``{` `    ``/* A Linked list node */``    ``static` `class` `Node``    ``{``        ``int` `data;``        ``Node next;``    ``};` `    ``// function to insert a node at the``    ``// beginning of the linked list``    ``static` `Node push(Node head_ref, ``int` `new_data)``    ``{``        ``/* allocate node */``        ``Node new_node = ``new` `Node();` `        ``/* put in the data */``        ``new_node.data = new_data;` `        ``/* link the old list to the new node */``        ``new_node.next = head_ref;` `        ``/* move the head to point to the new node */``        ``head_ref = new_node;``        ``return` `head_ref;``    ``}` `    ``// Function to count all pairs from both the linked lists``    ``// whose product is equal to a given value``    ``static` `int` `countPairs(Node head1, Node head2, ``int` `x)``    ``{``        ``int` `count = ``0``;` `        ``Node p1, p2;` `        ``// Traverse the 1st linked list``        ``for` `(p1 = head1; p1 != ``null``; p1 = p1.next)``        ``{``            ``// for each node of 1st list``            ``// Traverse the 2nd list``            ``for` `(p2 = head2; p2 != ``null``; p2 = p2.next)``            ``{``                ``// if sum of pair is equal to 'x'``                ``// increment count``                ``if` `((p1.data * p2.data) == x)``                ``{``                    ``count++;``                ``}``            ``}``        ``}` `        ``// required count of pairs``        ``return` `count;``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``Node head1 = ``null``;``        ``Node head2 = ``null``;` `        ``// create linked list1 3.1.5.7``        ``head1 = push(head1, ``7``);``        ``head1 = push(head1, ``5``);``        ``head1 = push(head1, ``1``);``        ``head1 = push(head1, ``3``);` `        ``// create linked list2 8.2.5.3``        ``head2 = push(head2, ``3``);``        ``head2 = push(head2, ``5``);``        ``head2 = push(head2, ``2``);``        ``head2 = push(head2, ``8``);` `        ``int` `x = ``10``;` `        ``System.out.print(``"Count = "` `+ countPairs(head1, head2, x));``    ``}``}` `// This code is contributed by Rajput-Ji`

## Python3

 `# Python3 program to count all pairs from both the``# linked lists whose product is equal to``# a given value`` ` `''' A Linked list node '''``class` `Node:``    ` `    ``def` `__init__(``self``, data):``        ``self``.data ``=` `data``        ``self``.``next` `=` `None``     ` `# function to insert a node at the``# beginning of the linked list``def` `push(head_ref, new_data):` `    ``''' allocate node '''``    ``new_node ``=` `Node(new_data)`` ` `    ``''' put in the data '''``    ``new_node.data ``=` `new_data;`` ` `    ``''' link the old list to the new node '''``    ``new_node.``next` `=` `(head_ref);`` ` `    ``''' move the head to point to the new node '''``    ``(head_ref) ``=` `new_node;``    ` `    ``return` `head_ref`` ` `# Function to count all pairs from both the linked lists``# whose product is equal to a given value``def` `countPairs(head1, head2, x):``    ``count ``=` `0``;   ``    ``p1 ``=` `head1``    ` `    ``# Traverse the 1st linked list``    ``while` `p1 !``=` `None``:       ``        ``p2 ``=` `head2``        ` `        ``# for each node of 1st list``        ``# Traverse the 2nd list``        ``while` `p2 !``=` `None``:       ``        ` `            ``# if sum of pair is equal to 'x'``            ``# increment count``            ``if` `((p1.data ``*` `p2.data) ``=``=` `x):``                ``count ``+``=` `1``            ``p2 ``=` `p2.``next``        ``p1 ``=` `p1.``next``        ` `    ``# required count of pairs``    ``return` `count;`` ` `# Driver Code``if` `__name__``=``=``'__main__'``:``    ` `    ``head1 ``=` `None``;``    ``head2 ``=` `None``;`` ` `    ``# create linked list1 3.1.5.7``    ``head1 ``=` `push(head1, ``7``);``    ``head1 ``=` `push(head1, ``5``);``    ``head1 ``=` `push(head1, ``1``);``    ``head1 ``=` `push(head1, ``3``);`` ` `    ``# create linked list2 8.2.5.3``    ``head2 ``=` `push(head2, ``3``);``    ``head2 ``=` `push(head2, ``5``);``    ``head2 ``=` `push(head2, ``2``);``    ``head2 ``=` `push(head2, ``8``);`` ` `    ``x ``=` `10``;`` ` `    ``print``(``"Count = "` `+` `str``(countPairs(head1, head2, x)))`` ` `# This code is contributed by rutvik_56`

## C#

 `// C# program to count all pairs from both the``// linked lists whose product is equal to``// a given value``using` `System;` `class` `GFG``{` `    ``/* A Linked list node */``    ``class` `Node``    ``{``        ``public` `int` `data;``        ``public` `Node next;``    ``};` `    ``// function to insert a node at the``    ``// beginning of the linked list``    ``static` `Node push(Node head_ref, ``int` `new_data)``    ``{``        ``/* allocate node */``        ``Node new_node = ``new` `Node();` `        ``/* put in the data */``        ``new_node.data = new_data;` `        ``/* link the old list to the new node */``        ``new_node.next = head_ref;` `        ``/* move the head to point to the new node */``        ``head_ref = new_node;``        ``return` `head_ref;``    ``}` `    ``// Function to count all pairs from both the linked lists``    ``// whose product is equal to a given value``    ``static` `int` `countPairs(Node head1, Node head2, ``int` `x)``    ``{``        ``int` `count = 0;` `        ``Node p1, p2;` `        ``// Traverse the 1st linked list``        ``for` `(p1 = head1; p1 != ``null``; p1 = p1.next)``        ``{``            ``// for each node of 1st list``            ``// Traverse the 2nd list``            ``for` `(p2 = head2; p2 != ``null``; p2 = p2.next)``            ``{``                ``// if sum of pair is equal to 'x'``                ``// increment count``                ``if` `((p1.data * p2.data) == x)``                ``{``                    ``count++;``                ``}``            ``}``        ``}` `        ``// required count of pairs``        ``return` `count;``    ``}` `    ``// Driver Code``    ``public` `static` `void` `Main(String[] args)``    ``{``        ``Node head1 = ``null``;``        ``Node head2 = ``null``;` `        ``// create linked list1 3->1->5->7``        ``head1 = push(head1, 7);``        ``head1 = push(head1, 5);``        ``head1 = push(head1, 1);``        ``head1 = push(head1, 3);` `        ``// create linked list2 8->2->5->3``        ``head2 = push(head2, 3);``        ``head2 = push(head2, 5);``        ``head2 = push(head2, 2);``        ``head2 = push(head2, 8);` `        ``int` `x = 10;` `        ``Console.Write(``"Count = "` `+ countPairs(head1, head2, x));``    ``}``}` `// This code is contributed by Rajput-Ji`

## Javascript

 ``
Output:
`Count = 1`

Time complexity : O(N^2)

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