From c25f746db67c545e7059576425831f3e37494f00 Mon Sep 17 00:00:00 2001
From: Waqar Hassan Khan <waqar.hassan866@gmail.com>
Date: Sun, 26 Sep 2021 20:45:46 +0600
Subject: [PATCH] chore(CSharp): added merge sort (#484)

---
 algorithms/CSharp/README.md                |  1 +
 algorithms/CSharp/src/Sorts/merge-sort.cs  | 67 ++++++++++++++++++++++
 algorithms/CSharp/test/Sorts/merge-sort.cs | 39 +++++++++++++
 docs/en/Sorting/Merge-Sort.md              |  1 +
 4 files changed, 108 insertions(+)
 create mode 100644 algorithms/CSharp/src/Sorts/merge-sort.cs
 create mode 100644 algorithms/CSharp/test/Sorts/merge-sort.cs

diff --git a/algorithms/CSharp/README.md b/algorithms/CSharp/README.md
index 109bb20e..3c818b97 100644
--- a/algorithms/CSharp/README.md
+++ b/algorithms/CSharp/README.md
@@ -7,6 +7,7 @@ For running the `.cs` file please using [.Net Finddle](https://dotnetfiddle.net/
 2. [Insertion Sort](src/Sorts/insertion-sort.cs)
 3. [Selection Sort](src/Sorts/selection-sort.cs)
 4. [Counting Sort](src/Sorts/counting-sort.cs)
+5. [Merge Sort](src/Sorts/merge-sort.cs)
 
 ## Strings
 - [Palindrome](src/Strings/palindrome.cs)
diff --git a/algorithms/CSharp/src/Sorts/merge-sort.cs b/algorithms/CSharp/src/Sorts/merge-sort.cs
new file mode 100644
index 00000000..05c34987
--- /dev/null
+++ b/algorithms/CSharp/src/Sorts/merge-sort.cs
@@ -0,0 +1,67 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Algorithms.Sorts
+{
+    public class MergeSort
+    {
+        public static List<int> Sort(List<int> numbers)
+        {
+            Divide(numbers, 0, numbers.Count - 1);
+            return numbers;
+        }
+
+        public static void Merge(List<int> numbers, int left, int mid, int right) 
+        {
+            List<int> leftPartition = new List<int>();
+            List<int> rightPartition = new List<int>();
+
+            for(int i = left; i <= mid; i++)
+            {
+                leftPartition.Add(numbers[i]);
+            }
+
+            for(int i = mid + 1; i <= right; i++)
+            {
+                rightPartition.Add(numbers[i]);
+            }
+
+            int l = 0, r = 0;
+            int size1 = leftPartition.Count, size2 = rightPartition.Count;
+
+            for(int i = left; i <= right; i++)
+            {
+                if((l < size1 && r >= size2) || (l < size1 && r < size2 && leftPartition[l] < rightPartition[r]))
+                {
+                    numbers[i] = leftPartition[l++];
+                }
+                else
+                {
+                    numbers[i] = rightPartition[r++];
+                }
+            }
+        }
+
+        public static void Divide(List<int> numbers, int left, int right)
+        {
+            if(left < right)
+            {
+                int mid = (left + right) / 2;
+
+                Divide(numbers, left, mid);
+                Divide(numbers, mid + 1, right);
+
+                Merge(numbers, left, mid, right);
+            }
+        }
+
+        public static void Main()
+        {
+            List<int> numbers = new List<int> { 9, 1, -1, 10, 12, 2, 0, 0, -2, -9 , 107};
+            List<int> answer = Sort(numbers);
+
+            Console.WriteLine(string.Join(", ", answer));
+        }
+    }
+}
diff --git a/algorithms/CSharp/test/Sorts/merge-sort.cs b/algorithms/CSharp/test/Sorts/merge-sort.cs
new file mode 100644
index 00000000..2a08872e
--- /dev/null
+++ b/algorithms/CSharp/test/Sorts/merge-sort.cs
@@ -0,0 +1,39 @@
+using NUnit.Framework;
+using System.Collections.Generic;
+
+namespace Algorithms.Tests.Sorts
+{
+    [TestFixture]
+    class MergeSort
+    {
+        static object[] TestCasesForMergeSort =
+        {
+            new object[] {
+                new List<int>{ 0, 19, 12, 22, 107, 118, 0, 1, 2},
+                "0, 0, 1, 2, 12, 19, 22, 107, 118"
+            },
+
+            new object[] {
+                new List<int>{ 10, 11, 19, 0, -1, -19, -12, 1, 2, 1, 16, -100},
+                "-100, -19, -12, -1, 0, 1, 1, 2, 10, 11, 16, 19"
+            },
+
+            new object[] {
+                new List<int>{ -1, -2, -3, -4, -5, -10},
+                "-10, -5, -4, -3, -2, -1"
+            },
+
+            new object[] { 
+                new List<int>{ -1 },
+                "-1"
+            }
+        };
+
+        [TestCaseSource(nameof(TestCasesForMergeSort))]
+        public void TestMergeSort_ShouldGetExpected(List<int> numbers, string expected)
+        {
+            List<int> results = Algorithms.Sorts.MergeSort.Sort(numbers);
+            Assert.AreEqual(string.Join(", ", results), expected);
+        }
+    }
+}
diff --git a/docs/en/Sorting/Merge-Sort.md b/docs/en/Sorting/Merge-Sort.md
index 02426d89..fce83fb5 100644
--- a/docs/en/Sorting/Merge-Sort.md
+++ b/docs/en/Sorting/Merge-Sort.md
@@ -24,6 +24,7 @@ Sorted array is
 - [C++](../../../algorithms/CPlusPlus/Sorting/merge-sort.cpp)
 - [JavaScript](../../../algorithms/JavaScript/src/sorting/merge-sort.js)
 - [Python](../../../algorithms/Python/sorting/merge_sort.py)
+- [C#](../../../algorithms/CSharp/src/Sorts/merge-sort.cs)
 
 ## Video URL