---
title: "permutation"
source: https://www.jemoka.com/posts/kbhpermutation/
---

A permutation \(\pi\) of some \(\{1,2,&hellip;, n\}\) is a rearrangement of this list. There are \(n!\) different permutations of this set.
A permutation is an ORDERED arrangement of objects.
permutation with indistinct objects What if you want to order a set with sub-set of indistinct objects? Like, for instance, how many ways are there to order:
\begin{equation} 10100 \end{equation}
For every permutation of \(1\) in this set, there are two copies being overcounted.
Let there are \(n\) objects. \(n_1\) objects are the indistinct, \(n_2\) objects are indistinct, &hellip; \(n_{r}\) objects are the same. The number of permutations are:
\begin{equation} \frac{n!}{{n_1}!{n_2}! \dots {n_r}!} \end{equation}
You can use iterators to give you permutations.
