Count pairs from two sorted arrays whose sum is equal to a given value x

Given two sorted arrays of size m and n of distinct elements. Given a value x. The problem is to count all pairs from both arrays whose sum is equal to x.
Note: The pair has an element from each array.

Examples :

Input : arr1[] = {1, 3, 5, 7}
        arr2[] = {2, 3, 5, 8}
        x = 10

Output : 2
The pairs are:
(5, 5) and (7, 3)

Input : arr1[] = {1, 2, 3, 4, 5, 7, 11} 
        arr2[] = {2, 3, 4, 5, 6, 8, 12} 
        x = 9

Output : 5

Method 1 (Naive Approach): Using two loops pick elements from both the arrays and check whether the sum of the pair is equal to x or not.

C++

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// C++ implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
#include <bits/stdc++.h>
using namespace std;
  
// function to count all pairs
// from both the sorted arrays 
// whose sum is equal to a given
// value
int countPairs(int arr1[], int arr2[], 
               int m, int n, int x)
{
    int count = 0;
      
    // generating pairs from 
    // both the arrays
    for (int i = 0; i < m; i++)
        for (int j = 0; j < n; j++)
  
            // if sum of pair is equal 
            // to 'x' increment count 
            if ((arr1[i] + arr2[j]) == x) 
                count++;
      
    // required count of pairs     
    return count;
}
  
// Driver Code
int main()
{
    int arr1[] = {1, 3, 5, 7};
    int arr2[] = {2, 3, 5, 8};
    int m = sizeof(arr1) / sizeof(arr1[0]);
    int n = sizeof(arr2) / sizeof(arr2[0]);
    int x = 10;
    cout << "Count = "
         << countPairs(arr1, arr2, m, n, x);
    return 0;     

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Java

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// Java implementation to count pairs from
// both sorted arrays whose sum is equal
// to a given value
import java.io.*;
  
class GFG {
          
    // function to count all pairs
    // from both the sorted arrays 
    // whose sum is equal to a given
    // value
    static int countPairs(int []arr1, 
             int []arr2, int m, int n, int x)
    {
        int count = 0;
          
        // generating pairs from 
        // both the arrays
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
      
                // if sum of pair is equal 
                // to 'x' increment count 
                if ((arr1[i] + arr2[j]) == x) 
                    count++;
          
        // required count of pairs 
        return count;
    }
      
    // Driver Code
  
    public static void main (String[] args)
    {
        int arr1[] = {1, 3, 5, 7};
        int arr2[] = {2, 3, 5, 8};
        int m = arr1.length;
        int n = arr2.length;
        int x = 10;
          
        System.out.println( "Count = "
        + countPairs(arr1, arr2, m, n, x));
    }
}
  
// This code is contributed by anuj_67.

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Python3

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# python implementation to count
# pairs from both sorted arrays 
# whose sum is equal to a given 
# value
  
# function to count all pairs from
# both the sorted arrays whose sum
# is equal to a given value
def countPairs(arr1, arr2, m, n, x):
    count = 0
  
    # generating pairs from both
    # the arrays
    for i in range(m):
        for j in range(n):
  
            # if sum of pair is equal
            # to 'x' increment count
            if arr1[i] + arr2[j] == x:
                count = count + 1
  
    # required count of pairs
    return count
  
# Driver Program
arr1 = [1, 3, 5, 7]
arr2 = [2, 3, 5, 8]
m = len(arr1)
n = len(arr2)
x = 10
print("Count = "
        countPairs(arr1, arr2, m, n, x))
  
# This code is contributed by Shrikant13.

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C#

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// C# implementation to count pairs from
// both sorted arrays whose sum is equal
// to a given value
using System;
  
class GFG {
          
    // function to count all pairs
    // from both the sorted arrays 
    // whose sum is equal to a given
    // value
    static int countPairs(int []arr1, 
            int []arr2, int m, int n, int x)
    {
        int count = 0;
          
        // generating pairs from 
        // both the arrays
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
      
                // if sum of pair is equal 
                // to 'x' increment count 
                if ((arr1[i] + arr2[j]) == x) 
                    count++;
          
        // required count of pairs 
        return count;
    }
      
    // Driver Code
  
    public static void Main ()
    {
        int []arr1 = {1, 3, 5, 7};
        int []arr2 = {2, 3, 5, 8};
        int m = arr1.Length;
        int n = arr2.Length;
        int x = 10;
          
        Console.WriteLine( "Count = "
        + countPairs(arr1, arr2, m, n, x));
    }
}
  
// This code is contributed by anuj_67.

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PHP

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<?php
// PHP implementation to count
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
  
  
// function to count all pairs 
// from both the sorted arrays
// whose sum is equal to a given
// value
function countPairs( $arr1, $arr2
                     $m, $n, $x)
{
    $count = 0;
      
    // generating pairs from
    // both the arrays
    for ( $i = 0; $i < $m; $i++)
        for ( $j = 0; $j < $n; $j++)
  
            // if sum of pair is equal 
            // to 'x' increment count 
            if (($arr1[$i] + $arr2[$j]) == $x
                $count++;
      
    // required count of pairs 
    return $count;
}
  
// Driver Code
$arr1 = array(1, 3, 5, 7);
$arr2 = array(2, 3, 5, 8);
$m = count($arr1);
$n = count($arr2);
$x = 10;
echo "Count = "
      countPairs($arr1, $arr2
                   $m,$n, $x);
  
// This code is contributed by anuj_67.
?>

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Output :

Count = 2

Time Complexity : O(mn)
Auxiliary space : O(1)



Method 2 (Binary Search): For each element arr1[i], where 1 <= i <= m, search the value (x – arr1[i]) in arr2[]. If search is successful, increment the count.

C++

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// C++ implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given
// value
#include <bits/stdc++.h>
using namespace std;
  
// function to search 'value' 
// in the given array 'arr[]' 
// it uses binary search technique 
// as  'arr[]' is sorted 
bool isPresent(int arr[], int low,
               int high, int value)
{
    while (low <= high)
    {
        int mid = (low + high) / 2;
          
        // value found
        if (arr[mid] == value)
            return true;     
              
        else if (arr[mid] > value) 
            high = mid - 1;
        else
            low = mid + 1; 
    }
      
    // value not found
    return false;
}
  
// function to count all pairs 
// from both the sorted arrays 
// whose sum is equal to a given
// value
int countPairs(int arr1[], int arr2[],
               int m, int n, int x)
{
    int count = 0;     
    for (int i = 0; i < m; i++)
    {
        // for each arr1[i]
        int value = x - arr1[i];
          
        // check if the 'value'
        // is present in 'arr2[]'
        if (isPresent(arr2, 0, n - 1, value))
            count++;
    }
      
    // required count of pairs     
    return count;
}
  
// Driver Code
int main()
{
    int arr1[] = {1, 3, 5, 7};
    int arr2[] = {2, 3, 5, 8};
    int m = sizeof(arr1) / sizeof(arr1[0]);
    int n = sizeof(arr2) / sizeof(arr2[0]);
    int x = 10;
    cout << "Count = "
         << countPairs(arr1, arr2, m, n, x);
    return 0;     
}

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Java

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// Java implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given
// value
import java.io.*;
class GFG {
  
// function to search 'value' 
// in the given array 'arr[]' 
// it uses binary search technique 
// as 'arr[]' is sorted 
static boolean isPresent(int arr[], int low,
                         int high, int value)
{
    while (low <= high)
    {
        int mid = (low + high) / 2;
          
        // value found
        if (arr[mid] == value)
            return true;     
              
        else if (arr[mid] > value) 
            high = mid - 1;
        else
            low = mid + 1
    }
      
    // value not found
    return false;
}
  
// function to count all pairs 
// from both the sorted arrays 
// whose sum is equal to a given
// value
static int countPairs(int arr1[], int arr2[],
                      int m, int n, int x)
{
    int count = 0
    for (int i = 0; i < m; i++)
    {
          
        // for each arr1[i]
        int value = x - arr1[i];
          
        // check if the 'value'
        // is present in 'arr2[]'
        if (isPresent(arr2, 0, n - 1, value))
            count++;
    }
      
    // required count of pairs 
    return count;
}
  
    // Driver Code
    public static void main (String[] args) 
    {
        int arr1[] = {1, 3, 5, 7};
        int arr2[] = {2, 3, 5, 8};
        int m = arr1.length;
        int n = arr2.length;
        int x = 10;
        System.out.println("Count = "
              + countPairs(arr1, arr2, m, n, x));
    }
}
  
// This code is contributed by anuj_67.

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Python 3

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# Python 3 implementation to count 
# pairs from both sorted arrays 
# whose sum is equal to a given
# value
  
# function to search 'value' 
# in the given array 'arr[]' 
# it uses binary search technique 
# as 'arr[]' is sorted 
def isPresent(arr, low, high, value):
  
    while (low <= high):
      
        mid = (low + high) // 2
          
        # value found
        if (arr[mid] == value):
            return True
              
        elif (arr[mid] > value) :
            high = mid - 1
        else:
            low = mid + 1
      
    # value not found
    return False
  
# function to count all pairs 
# from both the sorted arrays 
# whose sum is equal to a given
# value
def countPairs(arr1, arr2, m, n, x):
    count = 0
    for i in range(m):
        # for each arr1[i]
        value = x - arr1[i]
          
        # check if the 'value'
        # is present in 'arr2[]'
        if (isPresent(arr2, 0, n - 1, value)):
            count += 1
      
    # required count of pairs     
    return count
  
# Driver Code
if __name__ == "__main__":
    arr1 = [1, 3, 5, 7]
    arr2 = [2, 3, 5, 8]
    m = len(arr1)
    n = len(arr2)
    x = 10
    print("Count = ",
           countPairs(arr1, arr2, m, n, x))
  
# This code is contributed 
# by ChitraNayal

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C#

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// C# implementation to count pairs from both 
// sorted arrays whose sum is equal to a given
// value
using System;
  
class GFG {
  
    // function to search 'value' in the given
    // array 'arr[]' it uses binary search 
    // technique as 'arr[]' is sorted 
    static bool isPresent(int []arr, int low,
                         int high, int value)
    {
        while (low <= high)
        {
            int mid = (low + high) / 2;
              
            // value found
            if (arr[mid] == value)
                return true;     
                  
            else if (arr[mid] > value) 
                high = mid - 1;
            else
                low = mid + 1; 
        }
          
        // value not found
        return false;
    }
      
    // function to count all pairs 
    // from both the sorted arrays 
    // whose sum is equal to a given
    // value
    static int countPairs(int []arr1, int []arr2,
                             int m, int n, int x)
    {
        int count = 0; 
          
        for (int i = 0; i < m; i++)
        {
              
            // for each arr1[i]
            int value = x - arr1[i];
              
            // check if the 'value'
            // is present in 'arr2[]'
            if (isPresent(arr2, 0, n - 1, value))
                count++;
        }
          
        // required count of pairs 
        return count;
    }
  
    // Driver Code
    public static void Main () 
    {
        int []arr1 = {1, 3, 5, 7};
        int []arr2 = {2, 3, 5, 8};
        int m = arr1.Length;
        int n = arr2.Length;
        int x = 10;
        Console.WriteLine("Count = "
            + countPairs(arr1, arr2, m, n, x));
    }
}
  
// This code is contributed by anuj_67.

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PHP

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<?php
// PHP implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given
// value
  
// function to search 'value' 
// in the given array 'arr[]' 
// it uses binary search technique 
// as 'arr[]' is sorted 
function isPresent($arr, $low,
                   $high, $value)
{
    while ($low <= $high)
    {
        $mid = ($low + $high) / 2;
          
        // value found
        if ($arr[$mid] == $value)
            return true;     
              
        else if ($arr[$mid] > $value
            $high = $mid - 1;
        else
            $low = $mid + 1; 
    }
      
    // value not found
    return false;
}
  
// function to count all pairs 
// from both the sorted arrays 
// whose sum is equal to a given
// value
function countPairs($arr1, $arr2,
                    $m, $n, $x)
{
    $count = 0; 
    for ($i = 0; $i < $m; $i++)
    {
          
        // for each arr1[i]
        $value = $x - $arr1[$i];
          
        // check if the 'value'
        // is present in 'arr2[]'
        if (isPresent($arr2, 0, 
                      $n - 1, $value))
            $count++;
    }
      
    // required count of pairs 
    return $count;
}
  
    // Driver Code
    $arr1 = array(1, 3, 5, 7);
    $arr2 = array(2, 3, 5, 8);
    $m = count($arr1);
    $n = count($arr2);
    $x = 10;
    echo "Count = "
        , countPairs($arr1, $arr2, $m, $n, $x);
  
// This code is contributed by anuj_67.
?>

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Output :

Count = 2

Time Complexity : O(mlogn), searching should be applied on the array which is of greater size so as to reduce the time complexity.
Auxiliary space : O(1)

Method 3 (Hashing): Hash table is implemented using unordered_set in C++. We store all first array elements in hash table. For elements of second array, we subtract every element from x and check the result in hash table. If result is present, we increment the count.

C++

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// C++ implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
#include <bits/stdc++.h>
using namespace std;
  
// function to count all pairs 
// from both the sorted arrays 
// whose sum is equal to a given
// value
int countPairs(int arr1[], int arr2[], 
               int m, int n, int x)
{
    int count = 0;
      
    unordered_set<int> us;
      
    // insert all the elements 
    // of 1st array in the hash
    // table(unordered_set 'us')
    for (int i = 0; i < m; i++)
        us.insert(arr1[i]);
      
    // for each element of 'arr2[] 
    for (int j = 0; j < n; j++) 
  
        // find (x - arr2[j]) in 'us'
        if (us.find(x - arr2[j]) != us.end())
            count++;
      
    // required count of pairs     
    return count;
}
  
// Driver Code
int main()
{
    int arr1[] = {1, 3, 5, 7};
    int arr2[] = {2, 3, 5, 8};
    int m = sizeof(arr1) / sizeof(arr1[0]);
    int n = sizeof(arr2) / sizeof(arr2[0]);
    int x = 10;
    cout << "Count = "
         << countPairs(arr1, arr2, m, n, x);
    return 0;     
}

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Java

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import java.util.*;
// Java implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
  
class GFG
{
  
// function to count all pairs 
// from both the sorted arrays 
// whose sum is equal to a given 
// value 
static int countPairs(int arr1[], int arr2[], 
            int m, int n, int x) 
    int count = 0
      
    HashSet<Integer> us = new HashSet<Integer>();
      
    // insert all the elements 
    // of 1st array in the hash 
    // table(unordered_set 'us') 
    for (int i = 0; i < m; i++) 
        us.add(arr1[i]); 
      
    // for each element of 'arr2[] 
    for (int j = 0; j < n; j++) 
  
        // find (x - arr2[j]) in 'us' 
        if (us.contains(x - arr2[j])) 
            count++; 
      
    // required count of pairs 
    return count; 
  
// Driver Code 
public static void main(String[] args)
{
    int arr1[] = {1, 3, 5, 7}; 
    int arr2[] = {2, 3, 5, 8}; 
    int m = arr1.length; 
    int n = arr2.length; 
    int x = 10
    System.out.print("Count = "
        + countPairs(arr1, arr2, m, n, x));
}
}
  
// This code has been contributed by 29AjayKumar

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Python3

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# Python3 implementation to count 
# pairs from both sorted arrays 
# whose sum is equal to a given value 
  
# function to count all pairs from  
# both the sorted arrays whose sum
# is equal to a given value 
def countPairs(arr1, arr2, m, n, x):
    count = 0
    us = set()
  
    # insert all the elements 
    # of 1st array in the hash 
    # table(unordered_set 'us') 
    for i in range(m):
        us.add(arr1[i])
  
    # or each element of 'arr2[] 
    for j in range(n):
  
        # find (x - arr2[j]) in 'us' 
        if x - arr2[j] in us:
            count += 1
  
    # required count of pairs
    return count
  
# Driver code
arr1 = [1, 3, 5, 7]
arr2 = [2, 3, 5, 8]
m = len(arr1)
n = len(arr2)
x = 10
print("Count ="
       countPairs(arr1, arr2, m, n, x))
  
# This code is contributed by Shrikant13

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C#

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// C# implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
using System;
using System.Collections.Generic;
  
class GFG
{
  
// function to count all pairs 
// from both the sorted arrays 
// whose sum is equal to a given 
// value 
static int countPairs(int []arr1, int []arr2, 
            int m, int n, int x) 
    int count = 0; 
      
    HashSet<int> us = new HashSet<int>();
      
    // insert all the elements 
    // of 1st array in the hash 
    // table(unordered_set 'us') 
    for (int i = 0; i < m; i++) 
        us.Add(arr1[i]); 
      
    // for each element of 'arr2[] 
    for (int j = 0; j < n; j++) 
  
        // find (x - arr2[j]) in 'us' 
        if(us.Contains(x - arr2[j])) 
            count++; 
      
    // required count of pairs 
    return count; 
  
// Driver Code 
public static void Main(String[] args)
{
    int []arr1 = {1, 3, 5, 7}; 
    int []arr2 = {2, 3, 5, 8}; 
    int m = arr1.Length; 
    int n = arr2.Length; 
    int x = 10; 
    Console.Write("Count = "
        + countPairs(arr1, arr2, m, n, x));
}
}
  
// This code contributed by Rajput-Ji

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Output :

Count = 2

Time Complexity : O(m+n)
Auxiliary space : O(m), hash table should be created of the array having smaller size so as to reduce the space complexity.

Method 4 (Efficient Approach): This approach uses the concept of two pointers, one to traverse 1st array from left to right and another to traverse the 2nd array from right to left.

Algorithm :

countPairs(arr1, arr2, m, n, x)

     Initialize l = 0, r = n - 1
     Initialize count = 0

     loop while l = 0
        if (arr1[l] + arr2[r]) == x
           l++, r--
           count++
        else if (arr1[l] + arr2[r]) < x
           l++
        else
           r--

     return count 

C++

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// C++ implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
#include <bits/stdc++.h>
using namespace std;
  
// function to count all pairs 
// from both the sorted arrays 
// whose sum is equal to a given 
// value
int countPairs(int arr1[], int arr2[], 
               int m, int n, int x)
{
    int count = 0; 
    int l = 0, r = n - 1;
      
    // traverse 'arr1[]' from 
    // left to right
    // traverse 'arr2[]' from 
    // right to left
    while (l < m && r >= 0)
    {
        // if this sum is equal 
        // to 'x', then increment 'l', 
        // decrement 'r' and
        // increment 'count'
        if ((arr1[l] + arr2[r]) == x)
        {
            l++; r--;
            count++;         
        }
          
        // if this sum is less 
        // than x, then increment l
        else if ((arr1[l] + arr2[r]) < x)
            l++;
              
        // else decrement 'r' 
        else
            r--; 
    }
      
    // required count of pairs     
    return count;
}
  
// Driver Code
int main()
{
    int arr1[] = {1, 3, 5, 7};
    int arr2[] = {2, 3, 5, 8};
    int m = sizeof(arr1) / sizeof(arr1[0]);
    int n = sizeof(arr2) / sizeof(arr2[0]);
    int x = 10;
    cout << "Count = "
          << countPairs(arr1, arr2, m, n, x);
    return 0;     
}

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Java

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// Java implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
import java.io.*;
  
class GFG {
  
    // function to count all pairs 
    // from both the sorted arrays 
    // whose sum is equal to a given 
    // value
    static int countPairs(int arr1[], 
         int arr2[], int m, int n, int x)
    {
        int count = 0
        int l = 0, r = n - 1;
          
        // traverse 'arr1[]' from 
        // left to right
        // traverse 'arr2[]' from 
        // right to left
        while (l < m && r >= 0)
        {
              
            // if this sum is equal 
            // to 'x', then increment 'l', 
            // decrement 'r' and
            // increment 'count'
            if ((arr1[l] + arr2[r]) == x)
            {
                l++; r--;
                count++;         
            }
              
            // if this sum is less 
            // than x, then increment l
            else if ((arr1[l] + arr2[r]) < x)
                l++;
                  
            // else decrement 'r' 
            else
                r--; 
        }
          
        // required count of pairs 
        return count;
    }
      
    // Driver Code
    public static void main (String[] args) 
    {
        int arr1[] = {1, 3, 5, 7};
        int arr2[] = {2, 3, 5, 8};
        int m = arr1.length;
        int n = arr2.length;
        int x = 10;
        System.out.println( "Count = "
         + countPairs(arr1, arr2, m, n, x));
    }
}
  
// This code is contributed by anuj_67.

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Python3

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# Python 3 implementation to count
# pairs from both sorted arrays
# whose sum is equal to a given
# value
  
# function to count all pairs
# from both the sorted arrays
# whose sum is equal to a given
# value
def countPairs(arr1, arr2, m, n, x):
    count, l, r = 0, 0, n - 1
      
    # traverse 'arr1[]' from
    # left to right
    # traverse 'arr2[]' from
    # right to left
    while (l < m and r >= 0):
          
        # if this sum is equal
        # to 'x', then increment 'l',
        # decrement 'r' and
        # increment 'count'
        if ((arr1[l] + arr2[r]) == x):
            l += 1
            r -= 1
            count += 1
              
        # if this sum is less
        # than x, then increment l
        elif ((arr1[l] + arr2[r]) < x):
            l += 1
              
        # else decrement 'r'
        else:
            r -= 1
              
    # required count of pairs
    return count
  
# Driver Code
if __name__ == '__main__':
    arr1 = [1, 3, 5, 7]
    arr2 = [2, 3, 5, 8]
    m = len(arr1)
    n = len(arr2)
    x = 10
    print("Count =",
            countPairs(arr1, arr2,
                          m, n, x))
  
# This code is contributed 
# by PrinciRaj19992

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C#

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// C# implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
using System;
  
class GFG {
  
    // function to count all pairs 
    // from both the sorted arrays 
    // whose sum is equal to a given 
    // value
    static int countPairs(int []arr1, 
        int []arr2, int m, int n, int x)
    {
        int count = 0; 
        int l = 0, r = n - 1;
          
        // traverse 'arr1[]' from 
        // left to right
        // traverse 'arr2[]' from 
        // right to left
        while (l < m && r >= 0)
        {
              
            // if this sum is equal 
            // to 'x', then increment 'l', 
            // decrement 'r' and
            // increment 'count'
            if ((arr1[l] + arr2[r]) == x)
            {
                l++; r--;
                count++;         
            }
              
            // if this sum is less 
            // than x, then increment l
            else if ((arr1[l] + arr2[r]) < x)
                l++;
                  
            // else decrement 'r' 
            else
                r--; 
        }
          
        // required count of pairs 
        return count;
    }
      
    // Driver Code
    public static void Main () 
    {
        int []arr1 = {1, 3, 5, 7};
        int []arr2 = {2, 3, 5, 8};
        int m = arr1.Length;
        int n = arr2.Length;
        int x = 10;
        Console.WriteLine( "Count = "
        + countPairs(arr1, arr2, m, n, x));
    }
}
  
// This code is contributed by anuj_67.

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PHP

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<?php
// PHP implementation to count 
// pairs from both sorted arrays 
// whose sum is equal to a given 
// value
  
  
// function to count all pairs 
// from both the sorted arrays 
// whose sum is equal to a given 
// value
function  countPairs( $arr1$arr2
          $m$n$x)
{
     $count = 0; 
     $l = 0; $r = $n - 1;
      
    // traverse 'arr1[]' from 
    // left to right
    // traverse 'arr2[]' from 
    // right to left
    while ($l < $m and $r >= 0)
    {
        // if this sum is equal 
        // to 'x', then increment 'l', 
        // decrement 'r' and
        // increment 'count'
        if (($arr1[$l] + $arr2[$r]) == $x)
        {
            $l++; $r--;
            $count++;         
        }
          
        // if this sum is less 
        // than x, then increment l
        else if (($arr1[$l] + $arr2[$r]) < $x)
            $l++;
              
        // else decrement 'r' 
        else
            $r--; 
    }
      
    // required count of pairs     
    return $count;
}
  
// Driver Code
     $arr1 = array(1, 3, 5, 7);
     $arr2 = array(2, 3, 5, 8);
     $m = count($arr1);
     $n = count($arr2);
     $x = 10;
     echo "Count = "
    , countPairs($arr1, $arr2, $m, $n, $x);
// This code is contributed by anuj_67
  
?>

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Output :

Count = 2

Time Complexity : O(m + n)
Auxiliary space : O(1)

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