C++ Program for GCD 0.of more than two (or array) numbers?

Here we will see how we can get the gcd of more than two numbers. Finding gcd of two numbers are easy. When we want to find gcd of more than two numbers, we have to follow the associativity rule of gcd. For example, if we want to find gcd of {w, x, y, z}, then it will be {gcd(w,x), y, z}, then {gcd(gcd(w,x), y), z}, and finally {gcd(gcd(gcd(w,x), y), z)}. Using array it can be done very easily.

Algorithm

gcd(a, b)

begin
   if a is 0, then
      return b
   end if
   return gcd(b mod a, a)
end

getArrayGcd(arr, n)

begin
   res := arr[0]
   for i in range 1 to n-1, do
      res := gcd(arr[i], res)
   done
   return res;
end

Example

Live Demo

#include<iostream>
using namespace std;
int gcd(int a, int b) {
   if (a == 0)
      return b;
   return gcd(b%a, a);
}
int getArrayGcd(int arr[], int n) {
   int res = arr[0];
   for(int i = 1; i < n; i++) {
      res = gcd(arr[i], res);
   }
   return res;
}
main() {
   int arr[] = {4, 8, 16, 24};
   int n = sizeof(arr)/sizeof(arr[0]);
   cout << "GCD of array elements: " << getArrayGcd(arr, n);
}