Sort array using two thirds algorithm -


i came across uncommon sorting algorithm. algorithm sorts first 2/3rd of array next 2/3rd of array , again sorts first 2/3rd of array recursively.

fun sort3(a: int list): int list =   case of     nil => nil   | [x] => [x]   | [x,y] => [int.min(x,y), int.max(x,y)]   | => let       val n = list.length(a)       val m = (2*n+2) div 3       val res1 = sort3(list.take(a, m))       val res2 = sort3(list.drop(res1, n-m) @                        list.drop(a, m))       val res3 = sort3(list.take(res1, n-m) @                        list.take(res2, 2*m-n))     in       res3 @ list.drop(res2,2*m-n)     end

the recursive relation algorithm written 

t(n) = 2t(n/3) + o(n)

i dint understand how algo works.

what understand is, 1.it recursively calls same function until array size 3 sort array using bruteforce. 2. merge arrays (like in merge sort) using o(n) time.

am right?

i dont understand language written in, not understand code.can me understanding algorithm.

ps: not homework.


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