HackerRank.cs

using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.Serialization;
using System.Text.RegularExpressions;
using System.Text;
using System;

public class Solution
{

    public static void CountSort(int[] arr, int[] output, int[] count)
    {
        int n = arr.Length;

        for (int i = 0; i < count.Length; i++)
        {
            count[i] = 0;
        }

        // store count of each character 
        for (int i = 0; i < n; ++i)
        {
            ++count[arr[i]];
        }

        // Change count[i] so that count[i]  
        // now contains actual position of  
        // this character in output array 
        for (int i = 1; i < count.Length; ++i)
            count[i] += count[i - 1];

        // Build the output character array 
        // To make it stable we are operating in reverse order. 
        for (int i = n - 1; i >= 0; i--)
        {
            output[count[arr[i]] - 1] = arr[i];
            --count[arr[i]];
        }

    }


    // Complete the activityNotifications function below.
    static int activityNotifications_CountSort(int[] expenditure, int d)
    {
        int alerts = 0;
        int[] subSection = new int[d];
        int[] sortedSubSection = new int[d];
        int[] count = new int[200];
        int mid = d / 2;
        Array.Copy(expenditure, 0, subSection, 0, d);
        if (d % 2 == 0)
        {
            for (int i = d; i < expenditure.Length; i++)
            {
                subSection[d - (i % d) - 1] = expenditure[i];
                CountSort(subSection, sortedSubSection, count);

                int median = (sortedSubSection[mid] + sortedSubSection[mid + 1]) / 2;

                if (expenditure[i] >= (median * 2))
                {
                    alerts++;
                }
            }
        }
        else
        {
            for (int i = d; i < expenditure.Length; i++)
            {
                subSection[d - (i % d) - 1] = expenditure[i];
                CountSort(subSection, sortedSubSection, count);

                int median = sortedSubSection[mid];

                if (expenditure[i] >= (median * 2))
                {
                    alerts++;
                }
            }
        }
        return alerts;
    }
    static int activityNotifications_FirstAttempt(int[] expenditure, int d)
    {
        int alerts = 0;
        int[] subSection = new int[d];
        int mid = d / 2;
        for (int i = d; i < expenditure.Length; i++)
        {
            Array.Copy(expenditure, i - d,  subSection, 0, d);
            Array.Sort(subSection);

            int median;
            if (d % 2 == 0)
            {
                median = (subSection[mid] + subSection[mid + 1]) / 2;
            }
            else
            {
                median = subSection[mid];
            }

            if (expenditure[i] >= (median * 2))
            {
                alerts++;
            }
        }
        return alerts;

    }

    public static void PseduoMain(string[] args)
    {
        // this bit is given by HackerRank, but optimizations here will help too
        var lines = File.ReadAllLines(@"C:\code\TestSorting\input01.txt");
        string[] nd = lines[0].Split(' ');

        int n = Convert.ToInt32(nd[0]);

        int d = Convert.ToInt32(nd[1]);

        string[] items = lines[1].Split(' ');
        int[] expenditure = new int[items.Length];
        for (int i = 0; i < items.Length; i++)
        {
            expenditure[i] = Convert.ToInt32(items[i]);
        }

        int result = activityNotifications_CountSort(expenditure, d);

        Console.WriteLine("Result: " + result);
    }
}