Notes-TheAlgorithmDesignManual/selection_sort.org

• Selection Sort
  • Python
  • OCaml

Selection Sort

Runtime O(n²)

Python

def selection_sort(arr):
    sorted_list = []
    for i in range(len(arr)):
        max = arr[0]
        for count, value in enumerate(arr):
            if value > max:
                max = value
        sorted_list.append(max)
        arr.remove(max)
    return sorted_list

selection_sort([2,1,5,3,4])

OCaml

Really reinventing the wheel on this one…

let max_element = function
  | [] -> invalid_arg "empty list"
  | x::xs ->
     let rec f acc = function
       | [] -> acc
       | x::xs -> f (if x > acc then x else acc) xs
     in f x xs

let remove item list = 
  let rec f acc item = function
    | [] -> List.rev acc
    | x::xs -> if item = x then (List.rev acc) @ xs else f (x::acc) item xs
  in f [] item list

let selection_sort list =
  let rec f acc = function
    | [] -> acc
    | xs ->
       let m = max xs
       in f (m::acc) (remove m xs)
  in f [] list