Adde Pollards Rho algorithm (TheAlgorithms#365)

Author: damiansikora85

Algorithms.Tests/Other/PollardsRhoFactorizingTests.cs

@@ -0,0 +1,19 @@
+using Algorithms.Other;
+using NUnit.Framework;
+
+namespace Algorithms.Tests.Other
+{
+    public class PollardsRhoFactorizingTests
+    {
+        [TestCase(8051, 97)]
+        [TestCase(105, 21)]
+        [TestCase(253, 11)]
+        [TestCase(10403, 101)]
+        [TestCase(187, 11)]
+        public void SimpleTest(int number, int expectedResult)
+        {
+            var result = PollardsRhoFactorizing.Calculate(number);
+            Assert.AreEqual(expectedResult, result);
+        }
+    }
+}

Algorithms/Other/PollardsRhoFactorizing.cs

@@ -0,0 +1,37 @@
+using System;
+using Algorithms.Numeric.GreatestCommonDivisor;
+
+namespace Algorithms.Other
+{
+    /// <summary>Implementation of the Pollard's rho algorithm.
+    /// Algorithm for integer factorization.
+    /// Wiki: https://en.wikipedia.org/wiki/Pollard's_rho_algorithm.
+    /// </summary>
+    public static class PollardsRhoFactorizing
+    {
+        public static int Calculate(int number)
+        {
+            var x = 2;
+            var y = 2;
+            var d = 1;
+            var p = number;
+            var i = 0;
+            var gcd = new BinaryGreatestCommonDivisorFinder();
+
+            while (d == 1)
+            {
+                x = Fun_g(x, p);
+                y = Fun_g(Fun_g(y, p), p);
+                d = gcd.FindGcd(Math.Abs(x - y), p);
+                i++;
+            }
+
+            return d;
+        }
+
+        private static int Fun_g(int x, int p)
+        {
+            return (x * x + 1) % p;
+        }
+    }
+}

README.md

@@ -192,6 +192,7 @@ find more than one implementation for the same objective but using different alg
     * [Decisions Convolutions](./Algorithms/Other/DecisionsConvolutions.cs)
     * [Welford's Variance](./Algorithms/Other/WelfordsVariance.cs)
     * [Julian Easter](./Algorithms/Other/JulianEaster.cs)
+    * [Pollard's Rho](./Algorithms/Other/PollardsRhoFactorizing.cs)
   * [Problems](./Algorithms/Problems)
     * [Stable Marriage](./Algorithms/Problems/StableMarriage)
       * [Gale-Shapley](./Algorithms/Problems/StableMarriage/GaleShapley.cs)