Merge Sort in Octave

Welcome to the Merge Sort in Octave page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

function merge_sort()
    %input validation
    usage = 'Usage: please provide a list of at least two integers to sort in the format "1, 2, 3, 4, 5"';
    arg_list = argv();
    nargin = length(arg_list);
    if  nargin == 0
        %if there was no input
        disp(usage);
        return;
    end

    array_string = arg_list{1};
    array_size = sum(array_string == ',') + 1;
    if array_size < 2
        disp(usage);
        return;
    end

    %build array
    array = str2num(array_string);
    if length(array) ~= array_size || any(mod(array, 1) ~= 0)
        disp(usage);
        return;
    end

    %merge sort in ascending order
    array = MyMergeSort(array);

    %convert to string
    result_string = num2str(array);

    %replace space with ', '
    result_string = regexprep(result_string, '\s+', ', ');
    disp(result_string);
end

function [result] = MyMergeSort( x )
    % Sort vector 'x' using the merge sort algorithm
    % result is a vector consisting of the sorted values of 'x' 
    % in ascended order
    % Takes O( n log n ) time
    % Requires extra memory for merging results

    n = length(x);
    if n == 1
        % Stop the recursion, if we are down to one element in list
        result = x;
    else
        m = floor(n/2);  % Get the half way point

        r1 = MyMergeSort( x(1:m) );    % Sort first half recursively...
        r2 = MyMergeSort( x(m+1:n) );  % Sort 2nd half recursively...
        result = MyMerge( r1, r2 );    % Merge the two halves in sorted order
    end
end

function c = MyMerge( a, b )
    % Merges 2 vectors a,b into a result vector c 
    %   assumes a, b are already sorted
    %   'c' will also be in sorted order

    aLen = length(a);  % get length of a
    bLen = length(b);  % get length of b
    cLen = aLen+bLen;
    c = zeros(1,cLen); % pre-allocate 'c' to correct size

    % Initialize starting indices
    aIdx = 1;
    bIdx = 1;
    for cIdx = 1:cLen
        % Should we grab from 'a' or 'b' ???
        if aIdx > aLen
            % All done with 'a' vector, grab from 'b' vector.
            c(cIdx) = b(bIdx); 
            bIdx = bIdx + 1;
        elseif bIdx > bLen
            % All done with 'b' vector, grab from 'a' vector
            c(cIdx) = a(aIdx); 
            aIdx = aIdx + 1;
        elseif a(aIdx) <= b(bIdx)
            % a(i) <= b(i), grab from 'a' vector
            c(cIdx) = a(aIdx); 
            aIdx = aIdx + 1;
        else
            % b(i) < a(i), grab from 'b' vector
            c(cIdx) = b(bIdx); 
            bIdx = bIdx + 1;
        end
    end
end

% BY - Nikhil Gupta
% GitHub - nikkkhil067

Merge Sort in Octave was written by:

• rzuckerm

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

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