Count common elements in two arrays which are in Arithmetic Progression

// C# implementation to count the
// common elements of the two arithmetic
// progression of the given sequence
using System;
class GFG{

// Function to find GCD
static int gcd(int a,int b)
{
    if (b == 0)
        return a;
    return gcd(b, a % b);
}

// Function to find LCM
static int findlcm(int a, int b)
{
    int gc = gcd(a, b);
    return a * b / gc;
} 

// Function to count common element 
// of arr1[] and arr2[]
int CountCommon(int []arr1, 
                int []arr2, 
                int m, int n)
{
    
    // Common Difference
    int diff1 = arr1[1] - arr1[0];
    int diff2 = arr2[1] - arr2[0];

    // Function calling
    int lcm = findlcm(diff1, diff2);

    int ans1 = (arr1[m - 1] - arr1[0]) / lcm;
    int ans2 = (arr2[n - 1] - arr2[0]) / lcm;
    int ans = min(ans1, ans2);
    
    return (ans + 1);
} 

// Driver code
public static void Main()
{
    int []arr1 = { 2, 5, 8, 11, 14, 17 };
    int []arr2 = { 2, 4, 6, 8, 10, 12 };
    
    int m = arr1.Length;
    int n = arr2.Length;

    // Function calling
    Console.Write(CountCommon(arr1, arr2, m, n));
}
}

// This code is contributed by Code_Mech 

// Here is the  code in C# for the above approach
using System;

namespace CountCommonElements {
  class Program {
    // Function to check if x is present in the array or not
    static bool BinarySearch(int[] arr, int M, int x)
    {
      int l = 0, r = M - 1;
      while (l <= r) {
        int mid = (l + r) / 2;

        // Checking if the middle element is equal to x
        if (arr[mid] == x) {
          return true;
        }
        else if (arr[mid] < x) {
          l = mid + 1;
        }
        else {
          r = mid - 1;
        }
      }
      // Return true, if element x is present in the
      // array, else false
      return false;
    }

    // Function to count the number of elements common in
    // both the arrays
    static int CountCommon(int[] A, int[] B, int N, int M)
    {
      int count = 0;

      // Iterate each element of array A
      for (int i = 0; i < N; i++) {
        // Checking if the element of array A is present
        // in array B using the binary search
        if (BinarySearch(B, M, A[i])) {
          count++;
        }
      }
      // Return count of common elements
      return count;
    }

    // Driver Code
    static void Main(string[] args)
    {
      int[] A = { 2, 5, 8, 11, 14, 17 };
      int[] B = { 2, 4, 6, 8, 10, 12 };

      int N = A.Length;
      int M = B.Length;

      // Function call
      Console.WriteLine(CountCommon(A, B, N, M));
    }
  }
}

// This code is contributed by sarojmcy2e

using System;
using System.Collections.Generic;
using System.Linq;

class Program {
    // Function to count the number of common elements
    // between two lists
    static int CountCommonElements(List<int> arr1,
                                   List<int> arr2)
    {
        // Convert the two lists to hash sets to efficiently
        // find the common elements
        HashSet<int> setArr1 = new HashSet<int>(arr1);
        HashSet<int> setArr2 = new HashSet<int>(arr2);

        // Using the intersection operator & to find the
        // common elements
        int count = setArr1.Intersect(setArr2).Count();

        // Print the count of common elements
        Console.WriteLine(
            count); // prints the count using &

        // Return a dummy value since the function signature
        // specifies that it returns an integer
        return 0;
    }

    static void Main(string[] args)
    {
        // Define the two input lists
        List<int> arr1
            = new List<int>{ 2, 5, 8, 11, 14, 17 };
        List<int> arr2
            = new List<int>{ 2, 4, 6, 8, 10, 12 };

        // Call the CountCommonElements function and pass in
        // the two input lists
        CountCommonElements(arr1, arr2);

        // Wait for user input before exiting the program
        Console.ReadLine();
    }
}
// This code is contributed by sarojmcy2e