function cell = keygen(N,imin,imax,char,prob)

    cell = {};
    lenChar = length(char);
    
%validar args
    if nargin < 4
        error('wrong number of inputs')
    
    elseif nargin == 4
        prob(1,1:lenChar) = 0.5;
   
    else 
        lenProb = length(prob);
        if lenProb ~= lenChar
           error("Probability and Character array lengths don't match")
        end
    end
    
   
 %criar keys
     f = waitbar(0, 'Starting');    %made a waitbar since ex01a) asks for N=1e5 and char length 52. 
                                    %and the way i made this funtion..this is gonna take a while :_-)
                              
        for k = 1 : N
       
            lenKey = randi([imin,imax]);
            key = randsample(char,lenKey,true,prob);
            cell{k} = key;
      
            noDupe = unique(cell);

            %caso seja duplicado
            if numel(cell) ~= numel(noDupe)
                key = randsample(char,lenKey,true,prob);
                cell{k} = key;
                k = k-1;
            end

            waitbar(k/N, f, sprintf('Progress: %d %%', floor(k/N*100)));  %progress on the waitbar
            pause(0.01);
        end
      close(f)
  
end