public static int GetPermutation(InputValues value)
{
var nFact = GetFactorial(value.N);
if (nFact >= Int32.MaxValue)
throw new Exception("Result is too large.");
var nrFact = GetFactorial(value.N - value.R);
return nFact / nrFact;
}
public ActionResult Index(FormCollection collection)
{
int nn, rr;
var inputValues = new InputValues();
string n = collection["N"];
bool nOK = Int32.TryParse(n, out nn);
string r = collection["R"];
bool rOK = Int32.TryParse(r, out rr);
if (nOK && rOK)
{
inputValues = new InputValues() { N = nn, R = rr };
if (nn < rr)
{
ViewBag.Result = "n cannot be less than r.";
}
else
{
try
{
var result = 0;
var resultType = "";
var type = collection["hdnOperation"];
if (type.ToLower() == "per")
{
result = Calculator.GetPermutation(inputValues);
resultType = "P";
}
else
{
result = Calculator.GetCombination(inputValues);
resultType = "C";
}
ViewBag.Result = string.Format("<sub>{0}</sub>{1}<sub>{2}</sub> = {3}", nn, resultType, rr, result);
}
catch (Exception ex)
{
ViewBag.Result = ex.Message;
}
}
}
else
{
ViewBag.Result = "Please enter valid numbers for N and R.";
}
return View(inputValues);
}
public static int GetCombination(InputValues value)
{
return GetFactorial(value.N) / (GetFactorial(value.R) * GetFactorial(value.N - value.R));
}