Insertion Sort

What is an insertion sort?

A simple sorting algorithm which moves elements one at a time into the correct position, moving higher ranked elements up as necessary. It repeats until no input elements remain.

Which Big O?

O ( 1 ) = constant time (process time same regardless of array size)
O ( log n ) = log arithmetic (needs to be sorted)
O ( n ) = linear (i.e. twitter followers, increasing size takes longer)
O ( n log n ) = semi linear
O (n2) = quadratic (for loops)
O ( nk ) = polynomial
O ( Kn ) = Exponential time
O ( n! ) = factorial time

sudo code for algorithm

for i = 1 to n - 1 //loops over the index of the entry to be inserted
j = i
while j > 0 and A[j] < A[j - 1] // while loop performs the insertion
     swap(A[j], A[j - 1})  //swaps the element before as long as it is less
j = j - 1

The Code

How it works...

When to use it

Good

simplicity and efficiency
takes advantage of presorting
efficient for quite small data sets
more efficient in practice than most other simple quadratic algorithm such as selection sort or bubble sort

Bad

less efficient on large lists than more advanced algorithms such as quick sort, heap sort or merge sort

Resources

Good

http://en.wikipedia.org/wiki/Insertion_sort
http://www.sorting-algorithms.com/insertion-sort
http://rosettacode.org/wiki/Sorting_algorithms/Insertion_sort
https://www.youtube.com/watch?v=i-SKeOcBwko
http://bateru.com/news/2011/03/code-of-the-day-javascript-insertion-sort/