Task: Dutch national flag problem
C: #include <stdio.h> 
#include <stdlib.h> 
#include <stdbool.h> 
#include <time.h> 

#define NUMBALLS 5 

int compar(const void *a, const void *b){
	char c1=*(const char*)a, c2=*(const char*)b; 
	return c1-c2;
}

_Bool issorted(char *balls){
	int i,state;
	state=0;
	for(i=0;i<NUMBALLS;i++){
		if(balls[i]<state)return false;
		if(balls[i]>state)state=balls[i];
	}
	return true;
}

void printout(char *balls){
	int i;
	char str[NUMBALLS+1];
	for(i=0;i<NUMBALLS;i++)str[i]=balls[i]==0?'r':balls[i]==1?'w':'b';
	printf("%s\n",str);
}

int main(void) {
	char balls[NUMBALLS]; 
	int i;
	srand(time(NULL)); 
	rand(); 
	        
	
	for(i=0;i<NUMBALLS;i++)balls[i]=(double)rand()/RAND_MAX*3;
	while(issorted(balls)){ 
		printf("Accidentally still sorted: ");
		printout(balls);
		for(i=0;i<NUMBALLS;i++)balls[i]=(double)rand()/RAND_MAX*3;
	}
	printf("Non-sorted: ");
	printout(balls);
	qsort(balls,NUMBALLS,sizeof(char),compar); 
	if(issorted(balls)){ 
		printf("Sorted: ");
		printout(balls);
	} else {
		printf("Sort failed: ");
		printout(balls);
	}
	return 0;
}

C#: using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace RosettaCode
{
    class Program
    {
        static void QuickSort(IComparable[] elements, int left, int right)
        {
            int i = left, j = right;
            IComparable pivot = elements[left + (right - left) / 2];

            while (i <= j)
            {
                while (elements[i].CompareTo(pivot) < 0) i++;
                while (elements[j].CompareTo(pivot) > 0) j--;

                if (i <= j)
                {
                    
                    IComparable tmp = elements[i];
                    elements[i] = elements[j];
                    elements[j] = tmp;
                    i++;
                    j--;
                }
            }

            
            if (left < j) QuickSort(elements, left, j);
            if (i < right) QuickSort(elements, i, right);
        }
        const int NUMBALLS = 5;
        static void Main(string[] args)
        {
            Func<string[], bool> IsSorted = (ballList) =>
                {
                    int state = 0;
                    for (int i = 0; i < NUMBALLS; i++)
                    {
                        if (int.Parse(ballList[i]) < state)
                            return false;
                        if (int.Parse(ballList[i]) > state)
                            state = int.Parse(ballList[i]);
                    }
                    return true;
                };
            Func<string[], string> PrintOut = (ballList2) =>
                {
                    StringBuilder str = new StringBuilder();
                    for (int i = 0; i < NUMBALLS; i++)
                        str.Append(int.Parse(ballList2[i]) == 0 ? "r" : int.Parse(ballList2[i]) == 1 ? "w" : "b");
                    return str.ToString();
                };
            bool continueLoop = true;
            string[] balls = new string[NUMBALLS]; 
            Random numberGenerator = new Random();
            do 
            {
                
                for (int i = 0; i < NUMBALLS; i++)
                    balls[i] = numberGenerator.Next(3).ToString();

                continueLoop = IsSorted(balls);
                if (continueLoop)
                    Console.WriteLine("Accidentally still sorted: {0}", PrintOut(balls));
            } while (continueLoop);
            Console.WriteLine("Non-sorted: {0}", PrintOut(balls));
            QuickSort(balls, 0, NUMBALLS - 1); 
            Console.WriteLine("{0}: {1}", IsSorted(balls) ? "Sorted" : "Sort failed", PrintOut(balls));
        }
    }
}