/// <summary>
/// Euclidean algorithm for computing the GCD of two integers
/// </summary>
/// <param name="a">First number</param>
/// <param name="b">Second number</param>
/// <returns>GCD of two integers</returns>
public int CalculateGcd(int a, int b)
{
// If one number is zero, then the other will be a GCD
if (a == 0)
{
return(b);
}
if (b == 0)
{
return(a);
}
//If the numbers are negative, then the GCD is calculated from their absolute value
if (a < 0)
{
a = Math.Abs(a);
}
if (b < 0)
{
b = Math.Abs(b);
}
//The process repeats until the numbers become equal
while (a != b)
{
if (a > b)
{
AlghoritmHelper.Swap(ref a, ref b);
}
b -= a;
}
return(a);
}
/// <summary>
/// Finding the GCD of two numbers with the binary Euclidean algorithm
/// </summary>
/// <param name="a">First number</param>
/// <param name="b">Second number</param>
/// <returns>GCD of two numbers</returns>
public int CalculateGcd(int a, int b)
{
if (a == 0)
{
return(b);
}
if (b == 0)
{
return(a);
}
if (a == 1 || b == 1)
{
return(1);
}
//If the numbers are negative, then the GCD is calculated from their absolute value.
if (a < 0)
{
a = Math.Abs(a);
}
if (b < 0)
{
b = Math.Abs(b);
}
// shift - the largest power of two divided by a and b
int shift = 0;
while (((a | b) & 1) == 0)
{
shift++;
a >>= 1;
b >>= 1;
}
// Divide a by two until a becomes odd
while ((a & 1) == 0)
{
a >>= 1;
}
do
{
// If b is even, remove all factors 2 in b
while ((b & 1) == 0)
{
b >>= 1;
}
/* a and b are now odd.
* if you need to swap a and b,
* if necessary to satisfy the condition a <= b */
if (a > b)
{
AlghoritmHelper.Swap(ref a, ref b);
}
b -= a;
} while (b != 0);
// Restore degree a
return(a << shift);
}