highschool/Grade 10/Computer Science/ICS4U1/Sorting Methods/Insertion Sort.md

# Inssertion sort

## What is Insertion sort
- a sorting algorithm
- dividng an array into sroted and unsorted sections
- removes elements in idividually from un unosrted section of the list and inserts it into its correct position in a new sorted seqeuence

## Algorithm
- Set a key for the sections after the 1st element
- repeat the following
    - select first unsorted element as the key 
    - move sorted elements to the right to create space
    - shift unsorted elemnet into correct position
    - advance the key to the right by 1 element
- Tests first unsorted element (key) to last element of sorted section
- If key is larger, insertion sort leaves the element in place and hte next index's element becomes the key
- Else it finds the correct position within the sorted list
     - Duplicate the larger element in to one ahead of its current index each time the key is tested
     - By looping this, it makes space and inserts the key into that correct position

## Pseudo0code
```
for x = 1 : n
    key = list[x]
    y = x-1
    while y >= 0 && key < list[y]
        insert list[x] into the sorted sequence list[1 .. x-1]
        list[y+1] = list[y]
        y--
    list[y+1] = key
```