## insertion sort

### Data

in lua

#### Tags

insertion sort, sorting

### Source Code

``````-- Insertion sort algorithm
-- See: http://en.wikipedia.org/wiki/Insertion_sort#Algorithm

-- list: a list to be sorted, in-place
-- comp: (optional) a comparison function
--  defaults to function(a, b) return a < b end
-- returns: the passed-in list, sorted
return function (list, comp)
comp = comp or function(a, b) return a < b end
local n = #list
for i = 2, n do
local x = list[i]
local j = i
while j>1 and not comp(list[j-1],x) do
list[j] = list[j-1]
j = j - 1
end
list[j] = x
end
return list
end``````
``````-- Tests for insertion_sort.lua
local insertion_sort = require 'insertion_sort'

local total, pass = 0, 0

local function dec(str, len)
return #str < len
and str .. (('.'):rep(len-#str))
or str:sub(1,len)
end

local function run(message, f)
total = total + 1
local ok, err = pcall(f)
if ok then pass = pass + 1 end
local status = ok and 'PASSED' or 'FAILED'
print(('%02d. %68s: %s'):format(total, dec(message,68), status))
end

-- Comparison functions
local function le(a,b) return a <= b end
local function ge(a,b) return a >= b end

-- Checks if list is sorted
function is_sorted(list, comp)
comp = comp or le
for i = 2, #list do
if not comp(list[i-1],list[i]) then return false end
end
return true
end

-- Generates a table of n random values
local function gen(n)
local t = {}
for i = 1, n do t[i] = math.random(n) end
return t
end

math.randomseed(os.time())

run('Empty arrays', function()
local t = {}
assert(is_sorted(insertion_sort({})))
end)

local t = {1, 2, 3, 4, 5}
assert(is_sorted(insertion_sort(t)))
end)

run('Sorting a large array (1e3 values)', function()
local t = gen(1e3)
assert(is_sorted(insertion_sort(t)))
assert(is_sorted(insertion_sort(t, ge), ge))
end)

print(('-'):rep(80))
print(('Total : %02d: Pass: %02d - Failed : %02d - Success: %.2f %%')
:format(total, pass, total-pass, (pass*100/total)))
``````