nPr,permutation nPr, permutation [C#] yancyn Then /PreviewSnippet.aspx?SnippetID=025aa48f-e693-4c9c-9c7a-4b3eb4e0d4b7 SurroundsWith

/// Permutation. /// /// /// n n! /// P = __________ /// r (n-r)! /// /// n * (n-1) * (n-2) * (n-3) * ..... * (lower+1) * lower. /// /// /// /// /// private long nPr(long upper,long lower) { long output = 1; if(lower<1) lower = 1; for(long i=upper;i>=lower;i--) output *= i; return output; }]]>