using System;

using System.Collections.Generic;

using System.Text;

​

/// <summary>

/// Problem 1 Implement Singleton class

/// </summary>

public sealed class Singleton

{

    private static Singleton instance;

    private static object lockObject = new object();

    int _value;

    private Singleton(){}

    public static Singleton getInstance()

    {

        if (instance == null) {

            lock(lockObject) {

                if (instance == null) {

                    instance = new Singleton ();

                }

            }

        }

        return instance;

    }

    /// <summary>

    /// Gets or sets the value.

    /// </summary>

    /// <value>The value.</value>

    public int Value

    {

        get{ return _value;}

        set{ instance._value = value;}

    }

}

​

public class Program

{

    public static void Main (string[] args)

    {

        //Problem 1 Sort collection of Employee objects using employee's first name.

        List<Employee> employees = new List<Employee>();

        GenerateEmployees(ref employees);

        Console.WriteLine("\nProblem => Sort Employees in ascending order of name\nNon Sorted Employees");

        employees.Print();

        employees.Sort();

        //Or else we can also use LINQ to entities-method syntax

        //employees =  employees.OrderBy(emp => emp.FirstName).ToList<Employee>();

        Console.WriteLine("\nSorted Employees (By Name)");

        employees.Print();

        //Problem 2 Find numbers in string and sum the number. Example String "abce15def17,13bd4c"

        String str= "abce15def17,13bd4c";

        StringBuilder sb = new StringBuilder(str);

        Console.WriteLine("\nProblem => Add numbers present in a String\nInteger sum of \"{0}\" is : {1}", str,FindandAddNumber(sb));

    }

    /// <summary>

    /// Finds and adds the number present in the string recursively

    /// </summary>

    /// <returns>The sum of added number</returns>

    /// <param name="builder">Builder.</param>

    static int FindandAddNumber(StringBuilder builder)

    {

        int sum = 0;

        int numericalValue = 0;

        int charaterCount = 0;

        foreach (char c in builder.ToString()) {

            charaterCount++;

            // 48 is the ASCII value of charater '0'

            numericalValue = (int)c - 48;

            if ((numericalValue) > -1 && numericalValue < 10)

                sum = sum * 10 + numericalValue;

            else

                break;

        }

        builder.Remove(0,charaterCount);

        if (builder.Length > 0)

            return sum + FindandAddNumber(builder);

        else

            return sum;

    }

    /// <summary>

    /// Generates the employees.

    /// </summary>

    /// <param name="employees">Employees.</param>

    static void GenerateEmployees(ref List<Employee> employees)

    {

        Random rand = new Random();

        employees = new List<Employee>();

        for (int i = 0; i < 20; i++) {

            employees.Add (

                new Employee(){ 

                    EmpId = rand.Next()%100, 

                    FirstName = string.Format("{0}{1}{2}{3}",(Char)(65+rand.Next()%26),(Char)(65+rand.Next()%26),

                                              (Char)(65+rand.Next()%26), (Char)(65+rand.Next()%26))

                });

        }

    }

}

​

/// <summary>

/// Helper class to define extension method for peinting employees

/// </summary>

static class Helper

{

    public static void Print(this List<Employee> employees)

    {

        Console.WriteLine("******************");

        foreach(Employee emp in employees)

        {

            Console.WriteLine("Employee ID: "+emp.EmpId+ "\tEmployee Name: "+emp.FirstName);

        }

    }   

}

​

/// <summary>

/// Employee class specification

/// </summary>

class Employee:IComparable<Employee>

{

    int _empId;

    string _firstName;

    public string FirstName{

        get{return _firstName;}

        set{ _firstName = value;}

    }

    public int EmpId {

        get{ return _empId;}

        set{ _empId = value;}

    }

    #region IComparable implementation

    public int CompareTo (Employee other)

    {

        int scannedLength = 0;

        foreach (char c in FirstName) {

            if (other.FirstName.Length > scannedLength) {

                if (c > other.FirstName[scannedLength])

                    return 1;

                else if(c < other.FirstName[scannedLength])

                    return -1;

            } 

            else {

                return 1;

            }

            scannedLength++;

        }

        return 0;

    }

    #endregion

    public Employee()

    {

    }

}