104 lines
2.8 KiB
Lua
104 lines
2.8 KiB
Lua
if not integer_sort then
|
|
-- sorts input according to keys, changes ordering to permutation corresponding to new order
|
|
integer_sort = function(input, keys, ordering,temp_ordering, m) -- input, keys same length n, m = how many keys, O(2*n+m)
|
|
|
|
local n = #input;
|
|
local freq = {} -- frequencies of keys
|
|
local kpos = {} -- position of keys in sorted array
|
|
|
|
for i=1,n do -- count how many occurences - O(n)
|
|
local key = keys[ordering[i]]+1;
|
|
freq[key]=(freq[key] or 0)+1
|
|
temp_ordering[i]=ordering[i];
|
|
end
|
|
|
|
local curpos = 1;kpos[1]=1;
|
|
for i =1,m-1 do -- determine positions of keys in final sorted array - O(m)
|
|
curpos = curpos + (freq[i] or 0);
|
|
kpos[i+1]=curpos -- {2=3, 3 = 6,..., n-1 = 321}
|
|
end
|
|
|
|
-- actually place values here
|
|
for i = 1,n do -- O(n)
|
|
local key = keys[temp_ordering[i]]+1;
|
|
local pos = kpos[key];
|
|
ordering[pos] = temp_ordering[i];
|
|
kpos[key]=kpos[key]+1; -- move to next spot for that key place
|
|
end
|
|
end
|
|
|
|
permutate = function(input,ordering)
|
|
local output = {};
|
|
for i =1,#input do
|
|
output[i] = input[ordering[i]]
|
|
end
|
|
return output
|
|
end
|
|
|
|
get_digits = function(Num,d,base) -- number, how many digits, what base
|
|
local digits = {};
|
|
local num = Num;
|
|
local r;
|
|
for i = 1, d do
|
|
r = num % base;
|
|
digits[#digits+1] = r;
|
|
num = (num-r)/base
|
|
end
|
|
return digits
|
|
end
|
|
|
|
dumparr = function(array)
|
|
if _G.type(array) ~= "table" then return array end
|
|
local ret = "{";
|
|
for i =1,#array-1 do
|
|
ret = ret .. dumparr(array[i]) .. ","
|
|
end
|
|
ret = ret .. dumparr(array[#array])
|
|
return ret .. "}"
|
|
end
|
|
|
|
|
|
radix_sort = function(input,d,base) -- array of numbers; base is also number of keys = m, d = how many steps of sorting = number of digits for single number
|
|
|
|
out = out .."\nRADIX SORT\n\narray to be sorted " .. dumparr(input)
|
|
|
|
local n = #input;
|
|
local ordering = {}; local temp_ordering = {}; for i = 1, n do ordering[i]=i end
|
|
local keys = {};
|
|
local keylist = {};
|
|
for i = 1,n do
|
|
keylist[i] = get_digits(input[i],d,base)
|
|
end
|
|
|
|
|
|
out = out .."\nlist of keys - ".. d .. " digits of base " .. base .. " expansion of numbers : \n" ..
|
|
dumparr(keylist)
|
|
|
|
for step = 1, d do
|
|
for i =1,n do
|
|
keys[i] = keylist[i][step];
|
|
end
|
|
integer_sort(input, keys, ordering, temp_ordering, base)
|
|
|
|
out = out .."\n"..step .. ". pass integer_sort : " .. dumparr(permutate(input,ordering))
|
|
end
|
|
|
|
out = out .. "\nradix sort final result : " .. dumparr(permutate(input,ordering))
|
|
|
|
end
|
|
|
|
|
|
--input = {"a","b","c","d","e"}
|
|
--keys = {5,3,4,1,2}
|
|
--ordering = {}; temp_ordering = {}; for i = 1, #input do ordering[i]=i end
|
|
--m=5;
|
|
|
|
--integer_sort(input, keys, ordering, temp_ordering,m);
|
|
--say(string.gsub(_G.dump(ordering),"\n",""))
|
|
--say(string.gsub(_G.dump(permutate(input,ordering)),"\n",""))
|
|
out = ""; self.label("")
|
|
|
|
input = {23,42,15,8,87};
|
|
radix_sort(input,5,3) -- d, base
|
|
self.display_text(out,60,3)
|
|
end |