Print all combinations from 0000 to 9999 in C#

Question

Hi all, just wondering if anyone had an algorithm lying around that printed all possible combos from 0000 to 9999 (trying to crack code into old phone and new to learning C#)...Million thanks. Bela

Answer 1

Why complicate matters?

for (Int32 index = 0; index < 10000; index++)
    Console.Out.WriteLine(index.ToString("0000"));

Since you're commenting that you're outputting to a label, with linefeeds between each value, here's a better way:

List<String> values = new List<String>();
for (Int32 index = 0; index < 10000; index++)
    values.Add(index.ToString("0000"));
label1.Text = String.Join(
    Environment.NewLine,
    values.ToArray());

Try that and see if it gives you what you want.

Answer 2

Do you want to count to 9999?

Answer 3

for (int index = 0; index < 10000; index++)
{
    Console.WriteLine(index);
}

Answer 4

Like Lasse said, simply print them in sequence. But you can do even simpler with Linq;

Enumerable.Range(0, 9999).ToList().ForEach(Console.WriteLine);

You could avoid the "ToList" as well, if you had a helper function (which I normally would have in a Utilities class);

public static void ForEach<T>(this IEnumerable<T> elements, Action<T> action)
{
    foreach (var element in elements) { action(element); }
}

Note that this utility method is not strictly required for it to work, but would greatly diminish the memory requirements (since ToList actcually creates a list of all the numbers in memory).

Answer 5

WTF entry:

Console.WriteLine("0000"); 
Console.WriteLine("0001"); 
Console.WriteLine("0002"); 
Console.WriteLine("0003"); 

// snip everything in the middle

Console.WriteLine("9998"); 
Console.WriteLine("9999");

For those of you who are lacking of humor, don't try this at home.

Answer 6

if you want to print the leading zeros too:

for(int iC1 = 0; iC1 < 10000; iC1++)
{
 if(iC1 < 10)
 {
   Console.WriteLine("000" + iC1.ToString());
 }
 else if(iC1 < 100)
 {
   Console.WriteLine("00" + iC1.ToString());
 }
 else if(iC1 < 1000)
 {
   Console.WriteLine("0" + iC1.ToString());
 }
 else
 {
   Console.WriteLine(iC1.ToString());
 }
}

I know this solution is not elegant, but it's easyer to understand this way.

btw: you have to compile this as C# Console Application, not as Windows Forms Application.

Answer 7

I think Digitalex's solution is the most elegant but too memory-consuming.

Here's a better option:

foreach (var number in Enumerable.Range(0, 10000).Select(i => i.ToString("0000")))
    Console.WriteLine(number);