Math

Math

• ccchai

  Hi,
  Triple is defined at the end of the posted code, could you please post the complete error
  
  
  
  

• Janni J

  Hi,
  what you're looking for is permutation of 3 numbers. I don't have much time to explain it but check this page for the algorithm: http://csharpcomputing.com/Tutorials/Lesson7.htm
  
  If you don't understand it just ask and when I have more time I'll describe it.
  
  
  

• vanita

  Well... I didnt want to mark just one reply as the answer, because all of them were very appreciated. I thank you all very much for you reply for I could not find any help anywhere else. Thank you so much again.
  
  

• KK Wong

  I edit my previous post, there is 2 parts of source - one to be in method and one to be outside method definition.
  
  
  

• BillH

  Hi. Cool question, I hope the following helps.

  In ordered combinations one has the number of possibilities (in your case 0 - 10) and the number of places to fill (in your case 3). To find out how many possible combinations there are one can use the mathematical function factorial. It's suprising the C# Math library does not contain this function as it is used often in computer science. Not to worry though, it's a simple recurisvely defined function; below is my version.

  private int factorial(int theNumber)

  {

  if (theNumber <= 1)

  return 1;

  else

  return theNumber * (factorial(theNumber - 1));

  }

  This only gives you the number of combinations if the possibilities == the places. So what you need do is call factorial as follows to get the number of combinations given a set of places smaller than or equal to the possibilities(you'll have to define variables for the possibilities and places):

  int m_intNumberOfCombinations = factorial(theNumberOfPossibilities)

                                                  / factorial(theNumberOfPossibilities - theNumberOfPlaces);

  
  

• Dennisld

  Hi!
  
  Do you mean this
  

• hharding

  Hi GvS!

  Thanks for participation (and you right, Math class could contain more about Math...), but one thing I can't pass by - recursive methods. This is because it's not optimal to write such code, here is how it should be done:

  public static class MathEx

  {

  public static int Factorial(int iterations)

  {

  int result = 1;

  for (int i = 2; i <= iterations; i++)

  {

  result *= i;

  }

  return result;

  }

  }

  In this version, there is no method calls, so no overhead related to method calls. This will be much faster and optimal implementation. Every time you call method, local stack allocated, parameters transferred to method and all this include reading/writing memory, which is much slower than * operation in CPU. If you use for() - only 3 variables in memory required - iterations, i & result. They all will be placed into CPU registers and processed much faster.

  If you feel interested in performance & optimizations questions - check this thread and vote there: http://forums.microsoft.com/MSDN/ShowPost.aspx PostID=329219&SiteID=1

  
  
  

• Roberson

  If what you are looking for is output like:
  000
  001
  002
  ...
  
  the code below will do that. It takes as input the min and max value for each digit and the number of digits in the string.

  Please forgive the formatting. This is my first post and this is how the source pasted in. I couldn't insert tabs without directly editing the HTML and I was having a heck of a time with increase/decrease indent.

  Method Call:
  // Print the possible combinations of 3 digits between 3 and 5 inclusive
  PrintCombinations(3, 5, 3);
  

  public void PrintCombinations(int minValue, int maxValue, int count)
  {
  bool done = false;
  // The max value that any offset should be
  int maxOffset = maxValue - minValue;
  // Offsets for the individual digits
  int[] digitOffset = new int[count];
  int x = 0;

  // Loop while there is more to do
  while(!done)
  {

  // Reset the output string
  string output = "";

  // Print the current offset values
  for(x = 0; x < count; x++)
  {
  output += minValue + digitOffset[x];
  }

  Console.WriteLine(output);

  // Increment the offset values
  // Starting with the rightmost digit
  for(x = count - 1; x >= 0; x--)
  {
  if(digitOffset[x] == maxOffset)
  {

  // If the digit offset is equal to the
  // max offset, reset it to 0
  digitOffset[x] = 0;

  // We may or may not be done
  done = true;

  }
  else
  {

  // Otherwise increment the offset
  digitOffset[x]++;

  // As long as an offset was incremented
  // there is more work to do.
  done = false;
  break;

  }

  }

  }

  }

  Hope this helps.

  
  

• David B. P

  There's nothin inherent to the Math namespace to do what you want. do you want all combinations of the 3 specific numbers, or all the combinations of 3 numbers in the range 0-10
  
  

• webGov

  I tried copying and pasting that code snippet. But I get errors. For the Triple...It asks if I am missing an assembly reference. Could you explain further please.
  
  
• Math