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

Last Updated : 06 Feb, 2023
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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 <iostream>
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 
<script>
// javascript program to count all pairs from both the
// linked lists whose product is equal to
// a given value
    /* A Linked list node */
class Node {
    constructor(val) {
        this.data = val;
        this.next = null;
    }
}

    // function to insert a node at the
    // beginning of the linked list
    function push(head_ref , new_data) {
        /* allocate node */
var 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
    function countPairs(head1,  head2 , x) {
        var count = 0;

var 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
    
var head1 = null;
var 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);

        var x = 10;

        document.write("Count = " + countPairs(head1, head2, x));

// This code contributed by umadevi9616 
</script>

Output
Count = 1

Time complexity: O(N^2)

Auxiliary Space: O(1)


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