# 3.5.1.1.31 Permut

## Description

Minimum Origin Version Required: 2019 SR0

This function is used to calculate the number of permutations for a specified k elements from a given set with n elements, denoted by:

$P_{k,n} = n(n-1)(n-2)...(n-k+1)$

Please note that a permutation is different from a combination in which the combination is a set of elements regardless of the internal order, while the internal order in a permutation is significant. For example, in the 3 elements of "a, b, c", "ab" and "ba" are considered the same combination but two different permutations.

## Syntax

double Permut(int n, int k)

## Parameters

n

The number of elements in a given set. It must be a positive integer.

k

The number of elements in each permutation. It must be a positive integer and k < n.

## Return

Return the number of k-permutations from a given set with n elements.

## Example

permut(4, 2) = ;  // returns 12
permut(8, 2) = ;  // returns 56