Adv2015/D11.1/Program.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace D11._1
{
    class Program
    {
        static string Increment(string input)
        {
            if (input.Length == 0) return input;

            StringBuilder sb = new StringBuilder();

            var pos = input.Length - 1;
            var nchar = input[pos] + 1;

            if (nchar == 'i' || nchar == 'l' || nchar == 'o')
                nchar++;

            if (nchar > 'z')
            {
                nchar = 'a';
                var inc = Increment(input.Substring(0, pos));
                sb.Append(inc);
                sb.Append((char) nchar);
            }
            else
            {
                sb.Append(input.Substring(0, pos));
                sb.Append((char) nchar);
            }

            return sb.ToString();
        }

        static bool IsValid(string pwd)
        {
            bool hasIncreasing = false;
            bool hasForbiddenLettres = false;
            int repetitions = 0;
            bool repetitionExists = false;

            char last = '\0', lalast = '\0';
            int same = 1;
            foreach (var c in pwd)
            {
                if (c == 'i' || c == 'l' || c == 'o')
                {
                    hasForbiddenLettres = true;
                    break;
                }

                if (c == last) same++;
                else same = 1;

                if (same == 4) repetitionExists = true;
                if (repetitionExists == false && same == 2)
                {
                    repetitions++;
                    repetitionExists = repetitions >= 2;
                }

                if (lalast + 1 == last && last + 1 == c)
                    hasIncreasing = true;

                lalast = last;
                last = c;
            }

            return hasForbiddenLettres == false && hasIncreasing && repetitionExists;
        }

        static void Main(string[] args)
        {
            if (args.Length < 1) throw new ArgumentException();
            string input = args[0];

            input = NexPassword(input);
            Console.WriteLine($"The next password is : {input}");

            input = NexPassword(input);
            Console.WriteLine($"The next password is : {input}");
        }

        private static string NexPassword(string input)
        {
            bool isValid = false;
            do
            {
                input = Increment(input);
                isValid = IsValid(input);
            } while (isValid == false);
            return input;
        }
    }
}