Added Exponential Search and Tests

Tests/search/ExponentialSearchTests.cs

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+using System.Collections.Generic;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using csharp_algorithms;
+using exponentialsearch;
+
+namespace Tests.search
+{
+    [TestClass]
+    public class ExponentialSearchTest
+    {
+        [TestMethod]
+        public void Search()
+        {
+            // Setup
+            int[] arr = { 0, 1, 10, 13, 16, 20, 22, 28, 31, 39, 45, 55 };
+            int searchElem = 10;
+
+
+            // Search
+            var result1 = ExponentialSearch.Search(arr, searchElem);
+            searchElem = 11;
+            var result2 = ExponentialSearch.Search(arr, searchElem); ;
+
+            // Assert
+            Assert.AreEqual(true, result1);
+            Assert.AreEqual(false, result2);
+        }
+    }
+}

exponentialsearch/ExponentialSearchTests/ExponentialSearchTests.cs

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+using System.Collections.Generic;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+//using csharp_algorithms;
+using exponentialsearch;
+
+namespace Tests.search
+{
+    [TestClass]
+    public class ExponentialSearchTest
+    {
+        [TestMethod]
+        public void Search()
+        {
+            // Setup
+            int[] arr = { 0, 1, 10, 13, 16, 20, 22, 28, 31, 39, 45, 55 };
+            int searchElem = 10;
+
+
+            // Search
+            var result1 = ExponentialSearch.Search(arr, searchElem);
+            searchElem = 11;
+            var result2 = ExponentialSearch.Search(arr, searchElem); ;
+
+            // Assert
+            Assert.AreEqual(true, result1);
+            Assert.AreEqual(false, result2);
+        }
+    }
+}

exponentialsearch/ExponentialSearchTests/ExponentialSearchTests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.8.0" />
+    <PackageReference Include="MSTest.TestAdapter" Version="1.3.2" />
+    <PackageReference Include="MSTest.TestFramework" Version="1.3.2" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\exponentialsearch\exponentialsearch.csproj" />
+  </ItemGroup>
+
+</Project>

exponentialsearch/exponentialsearch.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.28010.2046
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "exponentialsearch", "exponentialsearch\exponentialsearch.csproj", "{D0929E76-9CBB-4114-A8E1-DAC86469231A}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ExponentialSearchTests", "ExponentialSearchTests\ExponentialSearchTests.csproj", "{33278F91-0695-4B3A-A2EA-C31DB15AC0F7}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{D0929E76-9CBB-4114-A8E1-DAC86469231A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D0929E76-9CBB-4114-A8E1-DAC86469231A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D0929E76-9CBB-4114-A8E1-DAC86469231A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D0929E76-9CBB-4114-A8E1-DAC86469231A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{33278F91-0695-4B3A-A2EA-C31DB15AC0F7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{33278F91-0695-4B3A-A2EA-C31DB15AC0F7}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{33278F91-0695-4B3A-A2EA-C31DB15AC0F7}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{33278F91-0695-4B3A-A2EA-C31DB15AC0F7}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {1CD73586-E288-4293-9D0B-73997DF04E73}
+	EndGlobalSection
+EndGlobal

exponentialsearch/exponentialsearch/ExponentialSearch.cs

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+using System;
+using System.Diagnostics;
+
+namespace exponentialsearch
+{
+    public class ExponentialSearch
+    {
+        /**
+         * Exponential Search method which defines a subset range from the 
+         * given array and looks for the element in it.
+         */
+        public static Boolean Search(int[] arr, int elem)
+        {
+            int last = arr.Length - 1;
+
+            if (last <= 0)
+                return false;
+
+            if (arr[0] == elem)
+                return true;
+
+            // Find the range in which we will be looking for the element
+            int i = 1;
+            while (i < last && arr[i] <= elem)
+                i *= 2;
+
+            return BinarySearchRecursive(arr, i / 2, Math.Min(i, last), elem);
+        }
+
+        /**
+         * Binary Search is implemented through a recursive approach. If the
+         * the elem is not found at the midIndex, the method is called again
+         * with readjusted left or right range.
+         */
+        public static Boolean BinarySearchRecursive(int[] arr, int leftRange, int rightRange,
+            int elem)
+        {
+            if (leftRange > rightRange)
+                return false;
+
+            // Calculate the middle of the range given. This way there is no overflow
+            // in case of a larger array. For more info:
+            // https://stackoverflow.com/questions/6735259/calculating-mid-in-binary-search
+            int midIndex = leftRange + (rightRange - leftRange) / 2;
+
+            // If element found, return index, otherwise adjust left or right range
+            if (arr[midIndex] == elem)
+                return true;
+            else if (elem < arr[midIndex])
+                return BinarySearchRecursive(arr, leftRange, midIndex - 1, elem);
+            else if (elem > arr[midIndex])
+                return BinarySearchRecursive(arr, midIndex + 1, rightRange, elem);
+            return false;
+        }
+
+        public static Boolean BinarySearchIterative(int[] arr, int leftRange, int rightRange,
+            int elem)
+        {
+            int midIndex = 0;
+            while (leftRange <= rightRange)
+            {
+                midIndex = leftRange + (rightRange - leftRange) / 2;
+
+                if (arr[midIndex] == elem)
+                    return true;
+                else if (elem < midIndex)
+                    rightRange = midIndex - 1;
+                else
+                    leftRange = midIndex + 1;
+            }
+
+            return false;
+        }
+
+        public static void Main()
+        {
+
+        }
+    }
+}

exponentialsearch/exponentialsearch/exponentialsearch.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+  </PropertyGroup>
+
+</Project>