Diffrent digits

Question

can anyone give an idea for how to write a code that said if a nubmer that was obtained by ReadLIne, has diffrent digits? thankes for helping.

Roy S · Answer

It is possible without strings (however, I don't really get why you don't want to use them). I just changed Vulpes code a bit. The digits are now obtained by dividing the number by 10 and taking the rest of that division as the digit. EDIT: Realised it was a bit silly to actually store the digits in a list/array... using System; class Program { static void Main() { bool[] used = new bool[10]; // all false by default Console.Write("Enter a number : "); int number = int.Parse(Console.ReadLine()); bool different = true; while (number > 0) { int digit = number % 10; number /= 10; if (used[digit]) { different = false; break; } else { used[digit] = true; } } if (different) { Console.WriteLine("Digits are different"); } else { Console.WriteLine("Digits are not different"); } Console.ReadKey(); } }

Vulpes · Answer

I'm glad that one of us was awake, yesterday, Roy ;) How I missed that I don't know! Matan did start a separate thread where he asked for a solution to this using both integers and doubles but it then got mysteriously deleted. Anyway, doubles are tricky given that they usually have an approximate representation within the machine. Consequently, when you start multiplying or dividing by 10, some of the lower order digits can change and mess up the program. The best solution I've been able to come up with is to convert the double to decimal which crystallizes the initial digits and after that arithmetic is exact: using System; using System.Numeric; class Program { static void Main() { bool[] used = new bool[10]; // all false by default Console.Write("Enter a number : "); double number = double.Parse(Console.ReadLine()); decimal num = (decimal)Math.Abs(number); // convert to decimal and ignore sign bool different = true; while (num != Decimal.Truncate(num)) num *= 10m; // move all digits to right of dp to left of dp Console.WriteLine("The digits are
"); while (num > 0m) { int digit = (int)(num % 10m); num /= 10m; num = Decimal.Truncate(num); Console.WriteLine(digit); // print out digits so we can see what's happening if (used[digit]) { different = false; break; } else { used[digit] = true; } } Console.WriteLine(); if (different) { Console.WriteLine("Digits are different"); } else { Console.WriteLine("Digits are not different"); } Console.ReadKey(); } }

Vulpes · Answer

I'll be very surprised if there is an algorithm which doesn't involve string processing - you would have to parse Console.ReadLine to a number in any case - but wait for further answers.

matan shark · Answer

I need an algorithm.

Vulpes · Answer

BTW, perhaps the easiest of all ways to do this is to use LINQ (VS 2008 or later). However, string processing is still being used under the hood: using System; using System.Collections.Generic; using System.Linq; class Program { static void Main() { Console.Write("Enter a number : "); string number = Console.ReadLine(); bool different = number.Distinct().Count() == number.Length; if (different) { Console.WriteLine("Digits are different"); } else { Console.WriteLine("Digits are not different"); } Console.ReadKey(); } }

Vulpes · Answer

Unless there's some clever algorithm, I can't think of a way of doing it without considering the individual digits in the string. Do you have anything in mind?

matan shark · Answer

is there a way not using string?

Vulpes · Answer

Here's a more traditional way of doing it, if you're still using VS 2005 or don't want to use HashSet for some reason: using System; class Program { static void Main() { bool[] used = new bool[10]; // all false by default Console.Write("Enter a number : "); string number = Console.ReadLine(); bool different = true; foreach(char digit in number) { int index = digit - 48; // '0' to '9' are ascii 48 to 57 if(used[index]) { different = false; break; } else { used[index] = true; } } if (different) { Console.WriteLine("Digits are different"); } else { Console.WriteLine("Digits are not different"); } Console.ReadKey(); } }

Vulpes · Answer

An easy way to do it is to read the numeric string entered into a HashSet which automatically excludes duplicates. If the number of elements in the HashSet is the same as the original number string, then the digits must be different. Here's a quick example of this technique (needs VS 2008 or later): using System; using System.Collections.Generic; class Program { static void Main() { Console.Write("Enter a number : "); string number = Console.ReadLine(); HashSet hs = new HashSet (number); // automatically removes duplicates if (hs.Count == number.Length) { Console.WriteLine("Digits are different"); } else { Console.WriteLine("Digits are not different"); } Console.ReadKey(); } }