Separate sequences (TheAlgorithms#121)

* Move Fibonacci sequence to separate namespace

* Update README.md

Algorithms.Tests/Sequences/FibonacciSequenceTests.cs

@@ -0,0 +1,18 @@
+using System.Linq;
+using System.Numerics;
+using Algorithms.Sequences;
+using NUnit.Framework;
+
+namespace Algorithms.Tests.Sequences
+{
+    public class FibonacciSequenceTests
+    {
+        [Test]
+        public void First10ElementsCorrect()
+        {
+            var sequence = new FibonacciSequence().Sequence;
+
+            Assert.AreEqual(new BigInteger[] { 0, 1, 1, 2, 3, 5, 8, 13, 21, 34 }, sequence.Take(10));
+        }
+    }
+}

Algorithms/Sequences/FibonacciSequence.cs

@@ -0,0 +1,40 @@
+using System.Collections.Generic;
+using System.Numerics;
+
+namespace Algorithms.Sequences
+{
+    /// <summary>
+    /// <para>
+    ///     Fibonacci sequence.
+    /// </para>
+    /// <para>
+    ///     Wikipedia: https://wikipedia.org/wiki/Fibonacci_number.
+    /// </para>
+    /// <para>
+    ///     OEIS: https://oeis.org/A000045.
+    /// </para>
+    /// </summary>
+    public class FibonacciSequence : ISequence
+    {
+        /// <summary>
+        /// Gets Fibonacci sequence.
+        /// </summary>
+        public IEnumerable<BigInteger> Sequence
+        {
+            get
+            {
+                yield return 0;
+                yield return 1;
+                BigInteger previous = 0;
+                BigInteger current = 1;
+                while (true)
+                {
+                    var next = previous + current;
+                    previous = current;
+                    current = next;
+                    yield return next;
+                }
+            }
+        }
+    }
+}

Algorithms/Sequences/ISequence.cs

@@ -0,0 +1,16 @@
+using System.Collections.Generic;
+using System.Numerics;
+
+namespace Algorithms.Sequences
+{
+    /// <summary>
+    /// Common interface for all integer sequences.
+    /// </summary>
+    public interface ISequence
+    {
+        /// <summary>
+        /// Gets sequence as enumerable.
+        /// </summary>
+        IEnumerable<BigInteger> Sequence { get; }
+    }
+}

README.md

@@ -25,7 +25,6 @@ This repository contains algorithms and data structures implemented in C# for ed
 			* [Euclidean GCD](./Algorithms/Numeric/GreatestCommonDivisor/EuclideanGreatestCommonDivisorFinder.cs)
 			* [Binary GCD](./Algorithms/Numeric/GreatestCommonDivisor/BinaryGreatestCommonDivisorFinder.cs)
 		* [Gauss-Jordan Elimination](./Algorithms/Numeric/GaussJordanElimination.cs)
-		* [Fibonacci Sequence](./Algorithms/Numeric/Fibonacci.cs)
 	* [Searches](./Algorithms/Search/)
 		* [A-Star](./Algorithms/Search/AStar/)
 		* [Binary](./Algorithms/Search/BinarySearcher.cs)
@@ -50,6 +49,8 @@ This repository contains algorithms and data structures implemented in C# for ed
 			* [Radix](./Algorithms/Sorters/Integer/RadixSorter.cs)
 		* [String](./Algorithms/Sorters/String)
 			* [MSD Radix](./Algorithms/Sorters/String/MsdRadixStringSorter.cs)
+	* [Sequences](./Algorithms/Sequences/)
+		* [A000045 Fibonacci](./Algorithms/Sequences/FibonacciSequence.cs)
 	* [String](./Algorithms/Strings/)
 		* [Longest Consecutive Character](./Algorithms/Strings/GeneralStringAlgorithms.cs)
 		* [Palindrome Checker](./Algorithms/Strings/palindrome.cs)