Ejemplo n.º 1
0
        /// <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);
        }
Ejemplo n.º 2
0
        /// <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);
        }