Bubble Sort in Erlang

Bubble sort is quite boring, but it becomes more interesting if you try to implement it in a functional language for telecom – Erlang.

We have a list of numbers, we need to sort it. bubble sort algorithm runs through the whole list, iterating, and comparing the number of pairs. Upon verification of the following occurs: a smaller number is added to the output list, or change the number of places in this list if the right is smaller bust continues with the next iteration number. This bypass is repeated as long as the list will no longer be replaced.

In practice it is not necessary to use due to the large time complexity – O (n ^ 2); I implemented it in Erlang language in an imperative style, but if you’re interested you can look for the best options:


-module(bubbleSort).
-export([main/1]).

startBubbleSort([CurrentHead|Tail]) ->
    compareHeads(CurrentHead, Tail, [], [CurrentHead|Tail]).

compareHeads(CurrentHead, [NextHead|Tail], [], OriginalList) ->   
    if
        CurrentHead < NextHead ->
            compareHeads(NextHead, Tail, [CurrentHead], OriginalList);
        true ->
            compareHeads(CurrentHead, Tail, [NextHead], OriginalList)
    end;
    
compareHeads(CurrentHead, [NextHead|Tail], OriginalOutputList, OriginalList) ->
    if
        CurrentHead < NextHead ->
            OutputList = OriginalOutputList ++ [CurrentHead],
            compareHeads(NextHead, Tail, OutputList, OriginalList);
        true ->
            OutputList = OriginalOutputList ++ [NextHead],
            compareHeads(CurrentHead, Tail, OutputList, OriginalList)
    end;
  
compareHeads(CurrentHead, [], OriginalOutputList, OriginalList) ->
    OutputList = OriginalOutputList ++ [CurrentHead],
    if
        OriginalList == OutputList ->
            io:format("OutputList: ~w~n", [OutputList]);
        true ->
            startBubbleSort(OutputList)
    end.
  
main(_) ->
    UnsortedList = [69,7,4,44,2,9,10,6,26,1],
    startBubbleSort(UnsortedList).

Install and run

In Erlang Ubuntu install is easy, just enter the following command in a terminal sudo apt install erlang. In this language, each file must be of a module (module), a list of functions that can be used outside – export. The interesting features of the language is the lack of variables, only constants, there is no standard syntax for the PLO (which does not prevent the use of OOP techniques), and of course the parallel computing without locks based on actor model.

Start module can be either through an interactive console erl, running one command after another, either through easier escript bubbleSort.erl; For different cases the file will look different, for example escript necessary to make the main function, from which it will start.

References

https://www.erlang.org/

https://habr.com/ru/post/197364/

Source Code

https://gitlab.com/demensdeum/algorithms/blob/master/bubbleSort/bubbleSort.erl

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