# Insertion-sort in Clojure

The next sorting algorithm I have decided to explore is the Insertion-sort.
This sorting technique can be completed in-place, however, using Clojure we will instead be using a `reduce`

to accumulate the final sorted collection.
Each element is iteratively inserted into a ‘new’ collection which maintains a sorted invariant as shown in the implementation documented below.

```
(defn insertion-sort [xs]
(letfn [(insert [col x]
(loop [[y & ys] col acc []]
(cond
(nil? y) (conj acc x)
(<= x y) (vec (concat acc [x y] ys))
:else (recur ys (conj acc y)))))]
(reduce insert [] xs)))
(insertion-sort [3 2 1]) ; [1 2 3]
```

The `reduce`

provides us with the infrastructure required around accumulating and iterating over each element within the provided collection.
The use of a private helper function gives us the ability to correctly insert the target element within the resulting collection.