Matlab - Queue data structure -
i working on implementing queue data structures using cell arrays in matlab. trying write functions advance queue one, search queue specific item. @ moment function looks (car types example data).
function q = createqueue() q={}; q = enqueue(q,'hilux'); q = enqueue(q,'e-type'); q = enqueue(q,'beetle'); q = enqueue(q,'enzo'); q = enqueue(q,'boxter'); q = dequeue(q) q = searchqueue(q,'boxter') end % adds item end of queue. returns new queue. function q = enqueue(q,item) q{end+1} = item; end function [q item] = dequeue(q) q{1} = {}; q{1} = q{2}; q{2} = q{3}; q{3} = q{4}; q{4} = q{5}; q{5} = {}; end function answer = searchqueue(q, item) = 1:length(q) if q{i} == item answer = fprintf('found @ index %d',i); break else disp('-1') end end end currently, dequeue function leaves empty cell, rather removing cell entirely. able avoided? searchqueue function returns error, , lost why. thanks
here's rough first cut @ using matlab's object oriented capabilities. reason creating class reference semantics handle type, allows dequeue/enqueue functions modify cell array directly, removing need reassignment.
i believe code example below answers main question how dequeue without leaving empty cell (could used without oop approach same effect).
to answer question what's wrong search: 1) comparison q{i} == item gives problems because == compares characters (which fails if there string size mismatch) whereas wanted use isequal(); 2) wanted sprintf rather fprintf; , 3) while not strictly wrong, else in loop happens on every item doesn't match, not wanted.
classdef queue < handle properties data = {} end methods function q = queue() % todo: in constructor if desired end function item = dequeue(q) % todo: bounds check item = q.data(1); q.data = q.data(2:end); end function enqueue(q,item) q.data{end+1} = item; end function answer = search(q, item) % todo: check multiple occurrences answer = 'not found'; = 1:length(q.data) if isequal(q.data{i},item) answer = sprintf('found @ index %d',i); break end end end end end 