F# and C# addings (#189)

* F# - Binary Search

* C# - Double selection sort

* quick sort - f#

01_introduction_to_algorithms/f#/Program.fs

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+// Learn more about F# at http://fsharp.org
+
+open System
+
+[<EntryPoint>]
+let main argv =
+    let numbers = [|1; 2; 3; 4; 5; 6; 7; 8; 9; 10|]
+
+    let rec binarySearch(arr: int[], number: int, startIndex: int, endIndex: int) : int
+        = 
+            let averageIndex = (startIndex + endIndex) / 2
+            let middleElement = arr.[averageIndex]
+
+            if (middleElement > number)
+                then binarySearch(arr, number, startIndex, averageIndex)
+            else if (middleElement < number)
+                then binarySearch(arr, number, averageIndex, endIndex)
+            else
+                averageIndex
+
+    let binarySearch(arr: int[], number: int)
+        = binarySearch(arr, number, 0, arr.Length)
+
+    let index = binarySearch(numbers, 7)
+    Console.WriteLine(index);
+    0

02_selection_sort/csharp/double_selection_sort/Program.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace SelectionSort
+{
+	class Program
+	{
+		static void Main(string[] args)
+		{
+			var numbers = new int[] { 4, 5, 1, 3, 10, 9, 6, 8, 7, 2 };
+			var sortedArr = SelectionSort(numbers);
+
+			Console.WriteLine(string.Join(',', sortedArr));
+		}
+
+		private static int[] SelectionSort(int[] array) 
+			=> SelectionSort(new LinkedList<int>(array)).ToArray();
+
+		private static IEnumerable<int> SelectionSort(LinkedList<int> list)
+		{
+			var minList = new LinkedList<int>();
+			var maxList = new LinkedList<int>();
+
+			while (list.Count != 0)
+			{
+				var min = list.Min();
+				list.Remove(min);
+				minList.AddLast(min);
+
+				var max = list.Max();
+				list.Remove(max);
+				maxList.AddFirst(max);
+			}
+
+			return minList.Union(maxList);
+		}
+	}
+}

04_quicksort/f#/QuickSort/Program.fs

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+// Learn more about F# at http://fsharp.org
+
+open System
+
+[<EntryPoint>]
+let main argv =
+    let numbers = [|3; 9; 10; 1; 4; 2; 6; 5; 8; 7|]
+
+    let rec quickSort(arr: int[]) =
+        if arr.Length < 2
+            then arr
+        else
+            let pivot = arr.[0]
+            let arrExcpetPivot = arr |> Seq.skip(1) |> Seq.toArray
+            let lessElements = quickSort arrExcpetPivot |> Seq.filter(fun n -> n <= pivot) |> Seq.toArray
+            let greaterElements = quickSort arrExcpetPivot |> Seq.filter(fun n -> n > pivot) |> Seq.toArray
+            
+            Seq.append (Seq.append lessElements [|pivot|]) greaterElements |> Seq.toArray
+
+    let sorted = quickSort(numbers)
+    0