From 60e49bfc46dbaa048f15e05df9425749df5f4982 Mon Sep 17 00:00:00 2001
From: Waqar Hassan Khan <waqar.hassan866@gmail.com>
Date: Sat, 18 Sep 2021 21:39:49 +0600
Subject: [PATCH] chore(CSharp): Added counting sort  (#470)

* added counting sort implementation

* updated readme

* added test case

* code refactored
---
 algorithms/CSharp/README.md                   |  3 +-
 algorithms/CSharp/src/Sorts/counting-sort.cs  | 69 +++++++++++++++++++
 algorithms/CSharp/test/Sorts/counting-sort.cs | 34 +++++++++
 3 files changed, 105 insertions(+), 1 deletion(-)
 create mode 100644 algorithms/CSharp/src/Sorts/counting-sort.cs
 create mode 100644 algorithms/CSharp/test/Sorts/counting-sort.cs

diff --git a/algorithms/CSharp/README.md b/algorithms/CSharp/README.md
index 081b254e..f16eb7f8 100644
--- a/algorithms/CSharp/README.md
+++ b/algorithms/CSharp/README.md
@@ -6,6 +6,7 @@ For running the `.cs` file please using [.Net Finddle](https://dotnetfiddle.net/
 1. [Bubble Sort](src/Sorts/bubble-sort.cs)
 2. [Insertion Sort](src/Sorts/insertion-sort.cs)
 3. [Selection Sort](src/Sorts/selection-sort.cs)
+4. [Counting Sort](src/Sorts/counting-sort.cs)
 
 ## Strings
 - [Palindrome](src/Strings/palindrome.cs)
@@ -20,7 +21,7 @@ For running the `.cs` file please using [.Net Finddle](https://dotnetfiddle.net/
 ## Queues
 - [Queue Implementation Using Two Stacks](src/Queues/queue-implementation-using-two-stacks.cs)
 
-## Recusrsion
+## Recursion
 - [Factorial](src/Recursion/factorial.cs)
 
 ## Graph
diff --git a/algorithms/CSharp/src/Sorts/counting-sort.cs b/algorithms/CSharp/src/Sorts/counting-sort.cs
new file mode 100644
index 00000000..73da37fa
--- /dev/null
+++ b/algorithms/CSharp/src/Sorts/counting-sort.cs
@@ -0,0 +1,69 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Algorithms.Sorts
+{
+    public class CountingSort
+    {
+        public static List<int> Sort(List<int> numbers)
+        {
+            int maxNumber = 0, minNumber = 0;
+            foreach(int number in numbers)
+            {
+                maxNumber = number > maxNumber ? number : maxNumber;
+                minNumber = number < minNumber ? number : minNumber;
+            }
+
+            int[] mx = Enumerable.Repeat(0, maxNumber + 1).ToArray();
+            int[] mn = Enumerable.Repeat(0, minNumber * -1 + 1).ToArray();
+
+            foreach(int number in numbers)
+            {
+                if(number >= 0)
+                {
+                    mx[number]++;
+                }
+
+                else
+                {
+                    mn[number * -1]++;
+                }
+            }
+
+            List<int> sortedList = new List<int>();
+
+            if(minNumber < 0)
+            {
+                for (int i = minNumber; i < 0; i++)
+                {
+                    while(mn[i * -1] > 0)
+                    {
+                        sortedList.Add(i);
+                        mn[i * -1]--;
+                    }
+                }
+            }
+
+            for(int i = 0; i <= maxNumber; i++)
+            {
+                while(mx[i] > 0)
+                {
+                    sortedList.Add(i);
+                    mx[i]--;
+                }
+            }
+
+            return sortedList;
+        }
+
+        public static void Main()
+        {
+            List<int> numbers = new List<int> { 9, 1, -1, 10, 12, 2, 0, 0, -2, -9 };
+            List<int> answer = Sort(numbers);
+
+            Console.WriteLine(string.Join(", ", answer));
+        }
+    }
+}
diff --git a/algorithms/CSharp/test/Sorts/counting-sort.cs b/algorithms/CSharp/test/Sorts/counting-sort.cs
new file mode 100644
index 00000000..9275df66
--- /dev/null
+++ b/algorithms/CSharp/test/Sorts/counting-sort.cs
@@ -0,0 +1,34 @@
+using NUnit.Framework;
+using System.Collections.Generic;
+
+namespace Algorithms.Tests.Sorts
+{
+    [TestFixture]
+    public class CountingSort
+    {
+        static object[] TestCasesForCountingSort =
+        {
+            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"
+            },
+        };
+
+        [TestCaseSource(nameof(TestCasesForCountingSort))]
+        public void TestCountingSort_ShouldGetExpected(List<int> numbers, string expected)
+        {
+            List<int> results = Algorithms.Sorts.CountingSort.Sort(numbers);
+            Assert.AreEqual(string.Join(", ", results), expected);
+        }
+    }
+}