comb sort


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by Yonaba

in lua

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-- Comb sort algorithm implementation
-- See: http://en.wikipedia.org/wiki/Comb_sort

-- Performs a Comb sort, in-place
-- list: a list of elements 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 in-place
return function (list, comp)
  comp = comp or function(a,b) return a<b end
  local gap = #list
  repeat
    gap = math.max(1, math.floor(gap/1.25))
    local i, swaps = 1, 0
    repeat
      if comp(list[i+gap], list[i]) and list[i]~=list[i+gap] then
        list[i], list[i+gap] = list[i+gap], list[i]
        swaps = 1
      end
      i = i+1
    until i+gap > #list
  until gap == 1 and swaps == 0
  return list
end
-- Tests for comb_sort.lua
local comb_sort = require 'comb_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)
  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 in [1..n]
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('Testing Comb sort', function()
  assert(is_sorted(comb_sort(gen(100), le), le))
  assert(is_sorted(comb_sort(gen(100), ge), ge))
end)

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