C#, how to find combinations

Question

1.00/5 (1 vote)

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hi, there is a problem with huge exponent.

example if I have the formula 2 pow n and n=2 then 2 pow 2=4

and the combinations are:

00
01
10
11

but what if n=100 ??? how to write code in c# for this solution...

thnx friends.

Posted 9-Dec-12 22:46pm

h5h6

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Comments

AnkitGoel.com 10-Dec-12 4:49am

what is the logic of generating these combinations? please explain.

[no name] 10-Dec-12 5:06am

Elaborate your question...

h5h6 10-Dec-12 5:26am

Yes, so there is a problem I cant write a code.
I want to write program only with that formula 2 pow n ( pow is for exponent )
I want to be generated all combinations for 2 pow 2 the result is 4
so the combinations are
00
01
10
11
for 2 pow 3 the resulat is 8
combnations:
000
001
010
101
101
011
111
110

so how to write code for this generation of combinations

2 solutions

Solution 2

I assume you mean that for 2ⁿ there are 4 possible bit combinations for n == 2, 8 for n == 3, and so forth.

To display the total combinations for a fixed value of n isn't complex - you just need a set of nested loops, one for each n - so n == 2needs two loops (one for the first bit, one for the second), and n == 3 needs 3.
But for any value of n, you can't specify the number of loops in advance, so you need to look at recursion. It's not complex, but since this smells badly of homework, I won't give you the code.

This about it: create a method which takes a number and a string as a parameter. It calls itself with the string + '0' and the number less one, then calls itself with the string + '1' and the number less one. (You will need to check for a termination here, and just print the string you are passed instead)

Try it, and see what you get...

Posted 9-Dec-12 23:32pm

OriginalGriff

Comments

h5h6 10-Dec-12 16:59pm

thnx, man.

OriginalGriff 11-Dec-12 2:47am

You're welcome!

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CPallini · Accepted Answer · 2012-12-09T23:21:00

Solution 1

You should go recursive (please note 2^100 is huge, so you need to be patient while waiting for the program to complete :-) ), e.g.

C#

static void bits(int[]  ab, int depth, int maxdept)
   {
     if (depth < maxdept)
     {
       ab[depth] = 0;
       bits(ab, depth + 1, maxdept);
       ab[depth] = 1;
       bits(ab, depth + 1, maxdept);
     }
     else
     {
       foreach (int i in ab)
       {
         Console.Write(i);
       }
       Console.WriteLine();
     }
   }

   public static void Main()
   {
     int[] ab;
     ab = new int[100];
     bits(ab, 0, 100);
   }

Posted 9-Dec-12 23:21pm

CPallini

Comments

h5h6 10-Dec-12 5:31am

haha for that, that is huge, I am looking for any other choice

CPallini 10-Dec-12 5:49am

I think you haven't another choice.

h5h6 10-Dec-12 17:44pm

why where i give the valu 10 ore more.... there are not all combinations....
example there is missig 000000000, 0000000001 ect,,

CPallini 10-Dec-12 18:12pm

The program actually produces full output, starting from 0000000000 and terminating with 1111111111. Since the ouput is 2^10=1024 lines long, you probably cannot scroll your console window to see it all (console buffer is limited).
Try to redirect the program output to a file (e.g. myprogram > out.txt) and then check out the file content.

h5h6 10-Dec-12 18:26pm

i can scroll so that is a problem....i see that there are not all generations

CPallini 10-Dec-12 18:34pm

You didn't you try to redirect the output, did you?
I just did: it worked has expected (you may also see the 0000000000 line using the debugger: put a breakpoint at Console.Writeline()).

h5h6 11-Dec-12 11:06am

I try to write code in windows form, i done it well but the generation are not horizontaly they are all vertical ex. n=2 there is
0
0

0
1

1
0

1
1

that is my code I cant do it to show generation horizontal lile :
00
01
10
11

private void btnKliko_Click(object sender, EventArgs e)
{

int[] ab;
int abc = int.Parse(textbox);
ab = new int[abc];
bits(ab, 0, abc);
}
public void bits(int[] ab, int depth, int maxdepth)
{
if (depth < maxdepth)
{
ab[depth] = 0;
bits(ab, depth + 1, maxdepth);
ab[depth] = 1;
bits(ab, depth + 1, maxdepth);

}
else
{
foreach (int i in ab)
{

lstGenertion.Items.Add(i);
}
}

CPallini 11-Dec-12 13:32pm

use:

else
{
StringBuilder sb = new StringBuilder();
foreach(int i in ab) sb.Append(i.Tostring());
lstGenertion.Items.Add(sb.Tostring());
}