using System;

using System.Text.RegularExpressions;

using System.Text;

using System.Collections.Generic;

public class Program

{

    //méthode qui remplace une chaine de caractere après des caractère

    public static string transformerChaine(string chaine){

        if (chaine != String.Empty){

            chaine=Regex.Replace(chaine,"a","R",RegexOptions.IgnoreCase);

            chaine=Regex.Replace(chaine , "c","Q",RegexOptions.IgnoreCase );

            chaine=Regex.Replace(chaine, "j","P", RegexOptions.IgnoreCase);

            return chaine;

        }else{

        return String.Empty  ;  }

        }

    public static char? premierCaracUniq(string chaine1) {

        if(chaine1 != String.Empty){

        for (int i = 0; i < chaine1.Length; i++) {

            String lettre = chaine1[i].ToString();      

            if (chaine1.IndexOf(lettre, StringComparison.OrdinalIgnoreCase) == chaine1.LastIndexOf(lettre, StringComparison.OrdinalIgnoreCase)) {

                return chaine1[i];

            }

        }

        return null;

        }else{

            return null;

            }

    }

    public static bool IsPalindrome(string valeur)

    {

        if(valeur != String.Empty){

        int min = 0;

        int max = valeur.Length - 1;

        while (true)

        {

            if (min > max)

            {

                return true;

            }

            char a = valeur[min];

            char b = valeur[max];

            if (char.ToLower(a) != char.ToLower(b))

            {

                return false;

            }

            min++;

            max--;

        }

        }else{

            return false;

            }

    }

    public static string InverserChaine(string source)

{

        if(source != String.Empty){

            var builder = new StringBuilder(source.Length);

                for (int i = source.Length - 1; i >= 0; i--)

            {

                builder.Append(source[i]);

            }

            return builder.ToString();

        }else{

            return null;

            }

}

    public static string InversMotChaine( string chaine3 ){

        if(chaine3 != String.Empty){

            string[] words = chaine3.Split(' ');

            Array.Reverse(words);

            chaine3 = String.Join(" ", words);

            return chaine3 ;

            }else{

            return null;

            }

    }

        public static char? caracImpair(string chaine4){

        if ( chaine4 != String.Empty){

            for (int i = 0; i < chaine4.Length; i++) { 

                int count = 0; 

            for (int j = 0; j < chaine4.Length; j++) { 

                if (chaine4[i] == chaine4[j]) 

                    count++; 

            } 

            if (count % 2 != 0) 

                return chaine4[i]; 

        } 

        return null; 

        }else{ return null ;}

        }

    public static Dictionary< char, int> occurenChaqCaractere(string chaine5 ){

        if( chaine5 != string.Empty){

            Regex rg = new Regex("[^a-zA-Z0-9]");

            chaine5 = rg.Replace(chaine5, "");

            Dictionary <char, int> dicoccurence = new Dictionary<char , int>();

            while (chaine5.Length > 0)

            {

                Console.Write(chaine5[0] + " : ");

                int count = 0;

                for (int j = 0; j < chaine5.Length; j++)

                {

                    if (chaine5[0] == chaine5[j])

                    {

                        count++;

                    }

                }

                 dicoccurence.Add(chaine5[0],count);

                Console.WriteLine(count);

                chaine5 = chaine5.Replace(chaine5[0].ToString(), string.Empty);

            }

            return dicoccurence;

        }else{

        return null;}

    }

​

    public static void Main()

    {

        Console.WriteLine("La nouvelle chaine est {0}",  transformerChaine("Abc"));

        Console.WriteLine("Le caractère unique est: {0}",premierCaracUniq("DFD"));

        Console.WriteLine("Palindrome ?{0} ",IsPalindrome("ici"));

        Console.WriteLine("La chaine inverser est :{0} ",InverserChaine("la vie est belle"));

        Console.WriteLine("Bonjour tout le monde   devient:  {0} ",InversMotChaine("Bonjour tout le monde"));

        Console.WriteLine("Le caractère avec le nombre d'occurence impair est : {0}",caracImpair("AABAC"));

        Console.WriteLine("Le nombre d'occurence de chaque caractère est: ");

        Dictionary <char, int> dicTest = new Dictionary<char, int>();

        dicTest = occurenChaqCaractere("aa@bbcc def");

    }

}