GCD

Calculates the greatest common divisor of the given numbers.

• Define a GCD() function for two numbers, which uses recursion.
• Base case is when y equals 0, which returns x.
• Otherwise the GCD of y and the remainder of the division x/y is returned.
• Define an overload that accepts multiple numbers or an array and use IEnumerable.Aggregate() to apply GCD() to them.

using System.Linq;

public static partial class _30s 
{
  public static int GCD(params int[] nums)
  {
    return nums.Aggregate(GCD);
  }
  public static int GCD(int x, int y)
  {
    return y == 0 ? x : GCD(y, x % y);
  }
}

_30s.GCD(8, 36, 28); // 4