Find element in array that divides all array elements

Given an array of n non-negative integers. Find such element in the array, that all array elements are divisible by it.

Examples :

Input : arr[] = {2, 2, 4}
Output : 2

Input : arr[] = {2, 1, 3, 1, 6}
Output : 1

Input: arr[] = {2, 3, 5}
Output : -1

The approach is to calculate GCD of the entire array and then check if there exist an element equal to the GCD of the array. For calculating the gcd of the entire array we will use Euclidean algorithm.

C++

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// CPP program to find such number in the array
// that all array elements are divisible by it
#include <bits/stdc++.h>
using namespace std;
  
// Returns gcd of two numbers.
int gcd(int a, int b)
{
    if (a == 0)
        return b;
    return gcd(b % a, a);
}
  
// Function to return the
// desired number if exists
int findNumber(int arr[], int n)
{
    // Find GCD of array
    int ans = arr[0];
    for (int i = 0; i < n; i++)
        ans = gcd(ans, arr[i]);
  
    // Check if GCD is present in array
    for (int i = 0; i < n; i++)
        if (arr[i] == ans)
            return ans;
  
    return -1;
}
  
// Driver Function
int main()
{
    int arr[] = { 2, 2, 4 };
    int n = sizeof(arr) / sizeof(arr[0]);
    cout << findNumber(arr, n) << endl;
    return 0;
}

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Java

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// JAVA program to find such number in
// the array that all array elements
// are divisible by it
import java.io.*;
  
class GFG {
  
    // Returns GCD of two numbers
    static int gcd(int a, int b)
    {
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }
  
    // Function to return the desired
    // number if exists
    static int findNumber(int arr[], int n)
    {
        // Find GCD of array
        int ans = arr[0];
        for (int i = 0; i < n; i++)
            ans = gcd(ans, arr[i]);
  
        // Check if GCD is present in array
        for (int i = 0; i < n; i++)
            if (arr[i] == ans)
                return ans;
  
        return -1;
    }
  
    // Driver Code
    public static void main(String args[])
    {
        int arr[] = { 2, 2, 4 };
        int n = arr.length;
        System.out.println(findNumber(arr, n));
    }
}
  
// This code is contributed by Nikita Tiwari

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Python3

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# Python3 program to find such number 
# in the array that all array 
# elements are divisible by it
  
# Returns GCD of two numbers
def gcd (a, b) :
    if (a == 0) :
        return b
      
    return gcd (b % a, a)
      
# Function to return the desired 
# number if exists
def findNumber (arr, n) :
  
    # Find GCD of array
    ans = arr[0]
    for i in range(0, n) :
        ans = gcd (ans, arr[i])
          
    # Check if GCD is present in array
    for i in range(0, n) :
        if (arr[i] == ans) :
            return ans
      
    return -1
      
# Driver Code
arr = [2, 2, 4];
n = len(arr)
print(findNumber(arr, n))
  
# This code is contributed by Nikita Tiwari

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C#

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// C# program to find such number in
// the array that all array elements
// are divisible by it
using System;
  
class GFG {
  
    // Returns GCD of two numbers
    static int gcd(int a, int b)
    {
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }
  
    // Function to return the desired
    // number if exists
    static int findNumber(int[] arr, int n)
    {
        // Find GCD of array
        int ans = arr[0];
        for (int i = 0; i < n; i++)
            ans = gcd(ans, arr[i]);
  
        // Check if GCD is present in array
        for (int i = 0; i < n; i++)
            if (arr[i] == ans)
                return ans;
  
        return -1;
    }
  
    // Driver Code
    public static void Main()
    {
        int[] arr = { 2, 2, 4 };
        int n = arr.Length;
        Console.WriteLine(findNumber(arr, n));
    }
}
  
// This code is contributed by vt_m

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PHP

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<?php
// PHP program to find such
// number in the array that
// all array elements are 
// divisible by it
  
// Returns gcd of two numbers
function gcd ($a, $b)
{
    if ($a == 0)
        return $b;
    return gcd ($b % $a, $a);
}
  
// Function to return the 
// desired number if exists
function findNumber ($arr, $n)
{
    // Find GCD of array
    $ans = $arr[0];
    for ($i = 0; $i < $n; $i++) 
        $ans = gcd ($ans, $arr[$i]);
      
    // Check if GCD is 
    // present in array
    for ($i = 0; $i < $n; $i++) 
        if ($arr[$i] == $ans)         
            return $ans;     
  
    return -1;
}
  
// Driver Code
$arr =array (2, 2, 4);
$n = sizeof($arr);
echo findNumber($arr, $n), "\n";
  
// This code is contributed by ajit
?>

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Output :

2


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Improved By : vt_m, jit_t