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# Count pairs from two arrays whose modulo operation yields K

• Difficulty Level : Basic
• Last Updated : 12 May, 2021

Given an integer and two arrays and , the task is to count the total pairs (formed after choosing an element from and another from ) from these arrays whose modulo operation yields Note: If in a pair (a, b), a > b then the modulo must be performed as a % b. Also, pairs occurring more than once will be counted only once.
Examples:

Input: arr1[] = {1, 3, 7}, arr2[] = {5, 3, 1}, K = 2
Output:
(3, 5) and (7, 5) are the only possible pairs.
Since, 5 % 3 = 2 and 7 % 5 = 2
Input: arr1[] = {2, 5, 99}, arr2[] = {2, 8, 1, 4}, K = 0
Output:
All possible pairs are (2, 2), (2, 8), (2, 4), (2, 1), (5, 1) and (99, 1).

Approach:

• Take one element from at a time and perform it’s modulo operation with all the other elements of one by one.
• If the result from the previous step is equal to then store the pair (a, b) in a set in order to avoid duplicates where a is the smaller element and b is the larger one.
• Total required pairs will be the size of the set in the end.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of above approach``#include ``using` `namespace` `std;` `// Function to return the total pairs``// of elements whose modulo yield K``int` `totalPairs(``int` `arr1[], ``int` `arr2[], ``int` `K, ``int` `n, ``int` `m)``{` `    ``// set is used to avoid duplicate pairs``    ``set > s;` `    ``for` `(``int` `i = 0; i < n; i++) {``        ``for` `(``int` `j = 0; j < m; j++) {` `            ``// check which element is greater and``            ``// proceed according to it``            ``if` `(arr1[i] > arr2[j]) {` `                ``// check if modulo is equal to K``                ``if` `(arr1[i] % arr2[j] == K)``                    ``s.insert(make_pair(arr1[i], arr2[j]));``            ``}``            ``else` `{``                ``if` `(arr2[j] % arr1[i] == K)``                    ``s.insert(make_pair(arr2[j], arr1[i]));``            ``}``        ``}``    ``}` `    ``// return size of the set``    ``return` `s.size();``}` `// Driver code``int` `main()``{``    ``int` `arr1[] = { 8, 3, 7, 50 };``    ``int` `arr2[] = { 5, 1, 10, 4 };``    ``int` `K = 3;``    ``int` `n = ``sizeof``(arr1) / ``sizeof``(arr1);``    ``int` `m = ``sizeof``(arr2) / ``sizeof``(arr2);` `    ``cout << totalPairs(arr1, arr2, K, n, m);``    ``return` `0;``}`

## Java

 `// Java implementation of above approach``import` `java.util.*;` `class` `GFG``{``    ``static` `class` `pair``    ``{``        ``int` `first, second;``        ``public` `pair(``int` `first, ``int` `second)``        ``{``            ``this``.first = first;``            ``this``.second = second;``        ``}``    ``}``    ` `    ``// Function to return the total pairs``    ``// of elements whose modulo yield K``    ``static` `int` `totalPairs(``int` `[]arr1, ``int` `[]arr2,``                          ``int` `K, ``int` `n, ``int` `m)``    ``{``    ` `        ``// set is used to avoid duplicate pairs``        ``HashSet s = ``new` `HashSet();``    ` `        ``for` `(``int` `i = ``0``; i < n; i++)``        ``{``            ``for` `(``int` `j = ``0``; j < m; j++)``            ``{``    ` `                ``// check which element is greater and``                ``// proceed according to it``                ``if` `(arr1[i] > arr2[j])``                ``{``    ` `                    ``// check if modulo is equal to K``                    ``if` `(arr1[i] % arr2[j] == K)``                        ``s.add(``new` `pair(arr1[i], arr2[j]));``                ``}``                ``else``                ``{``                    ``if` `(arr2[j] % arr1[i] == K)``                        ``s.add(``new` `pair(arr2[j], arr1[i]));``                ``}``            ``}``        ``}``    ` `        ``// return size of the set``        ``return` `s.size();``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `main(String []args)``    ``{``        ``int` `[]arr1 = { ``8``, ``3``, ``7``, ``50` `};``        ``int` `[]arr2 = { ``5``, ``1``, ``10``, ``4` `};``        ``int` `K = ``3``;``        ``int` `n = arr1.length;``        ``int` `m = arr2.length;``    ` `        ``System.out.println(totalPairs(arr1, arr2, K, n, m));``    ``}``}` `// This code is contributed by Princi Singh`

## Python3

 `# Python3 implementation of above approach` `# Function to return the total pairs``# of elements whose modulo yield K``def` `totalPairs(arr1, arr2, K, n, m):` `    ``# set is used to avoid duplicate pairs``    ``s``=``{}` `    ``for` `i ``in` `range``(n):``        ``for` `j ``in` `range``(m):` `            ``# check which element is greater and``            ``# proceed according to it``            ``if` `(arr1[i] > arr2[j]):` `                ``# check if modulo is equal to K``                ``if` `(arr1[i] ``%` `arr2[j] ``=``=` `K):``                    ``s[(arr1[i], arr2[j])]``=``1``            ``else``:``                ``if` `(arr2[j] ``%` `arr1[i] ``=``=` `K):``                    ``s[(arr2[j], arr1[i])]``=``1`   `    ``# return size of the set``    ``return` `len``(s)` `# Driver code` `arr1 ``=` `[ ``8``, ``3``, ``7``, ``50` `]``arr2 ``=` `[``5``, ``1``, ``10``, ``4` `]``K ``=` `3``n ``=` `len``(arr1)``m ``=` `len``(arr2)` `print``(totalPairs(arr1, arr2, K, n, m))` `# This code is contributed by mohit kumar 29`

## C#

 `// C# implementation of the approach``using` `System;``using` `System.Collections.Generic;``    ` `class` `GFG``{``    ``public` `class` `pair``    ``{``        ``public` `int` `first, second;``        ``public` `pair(``int` `first, ``int` `second)``        ``{``            ``this``.first = first;``            ``this``.second = second;``        ``}``    ``}``    ` `    ``// Function to return the total pairs``    ``// of elements whose modulo yield K``    ``static` `int` `totalPairs(``int` `[]arr1, ``int` `[]arr2,``                          ``int` `K, ``int` `n, ``int` `m)``    ``{``    ` `        ``// set is used to avoid duplicate pairs``        ``HashSet s = ``new` `HashSet();``    ` `        ``for` `(``int` `i = 0; i < n; i++)``        ``{``            ``for` `(``int` `j = 0; j < m; j++)``            ``{``    ` `                ``// check which element is greater and``                ``// proceed according to it``                ``if` `(arr1[i] > arr2[j])``                ``{``    ` `                    ``// check if modulo is equal to K``                    ``if` `(arr1[i] % arr2[j] == K)``                        ``s.Add(``new` `pair(arr1[i], arr2[j]));``                ``}``                ``else``                ``{``                    ``if` `(arr2[j] % arr1[i] == K)``                        ``s.Add(``new` `pair(arr2[j], arr1[i]));``                ``}``            ``}``        ``}``    ` `        ``// return size of the set``        ``return` `s.Count;``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `Main(String []args)``    ``{``        ``int` `[]arr1 = { 8, 3, 7, 50 };``        ``int` `[]arr2 = { 5, 1, 10, 4 };``        ``int` `K = 3;``        ``int` `n = arr1.Length;``        ``int` `m = arr2.Length;``    ` `        ``Console.WriteLine(totalPairs(arr1, arr2, K, n, m));``    ``}``}` `// This code is contributed by PrinciRaj1992`

## Javascript

 `   `
Output:
`3`

Note: To print all the pairs just print the elements of set.

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