How can I correct this error?

Write function called huge_add that adds together two positive integers of any length specified as strings using decimal notation. The single output argument is the result and it is a string as well. The inputs and output must contain digits only; no commas, spaces or any other characters are allowed. If any of these assumptions are violated by the input, the function returns the number -1.

Here is my code:

function[c]=huge_add(a1,b1)
aaa=length(a1);
bbb=length(b1);
c=0;
if isnumeric(a1) ||isnumeric(b1)
    c=-1
else if ~isnumeric(a1) ||~isnumeric(b1)
for i=1:aaa
    if a1(i)~='1'&& a1(i)~='2'&&a1(i)~='3'&&a1(i)~='4'&&a1(i)~='5'&&a1(i)~='6'&&a1(i)~='7'&&a1(i)~='8'&&a1(i)~='9'&&a1(i)~='0'
        c=-1
    end
end
for i=1:bbb
    if  b1(i)~='1'&&b1(i)~='2'&&b1(i)~='3'&&b1(i)~='4'&&b1(i)~='5'&&b1(i)~='6'&&b1(i)~='7'&&b1(i)~='8'&&b1(i)~='9'&&b1(i)~='0'
        c=-1
    end
end
    end
a=a1;
b=b1;
aa=length(a);
bb=length(b);
    as=(str2num(a));
    bs=(str2num(b));
    af=fliplr(a);
    bf=fliplr(b);
    if c~=-1
    if aa<bb
    for ii=1:aa
        x(ii)=af(ii);
        y(ii)=bf(ii);
        z(ii)=str2num(x(ii))+str2num(y(ii));
        zz{ii}=num2str(z(ii));
    end
    cl=fliplr(z);
    rem=(b(1):b(bb-aa));
    ca=[rem,cl(1):cl(end)];
    else if aa>bb
            for ii=1:bb
        x(ii)=af(ii);
        y(ii)=bf(ii);
        z(ii)=str2num(x(ii))+str2num(y(ii));
        zz(ii)=num2str(z(ii))
            end
    cl=fliplr(z);
    rem=(a(1):a(aa-bb));
    ca=[rem,cl(1):cl(end)];

      else
    for ii=1:aa
          x(ii)=af(ii);
          y(ii)=bf(ii);
          z(ii)=str2num(x(ii))+str2num(y(ii));
          zz(ii)=num2str(z(ii));
      end
      cl=fliplr(z);
      rem=[];
      ca=[rem,cl(1):cl(end)];
          end
      end
      d=str2num([rem,fliplr(zz)])

      %d=([rem,fliplr(zz)])
      c=num2str(d)
      end 

end

end

when the arguments are long numbers such as:'387363715250650494', '2959321308593705578801966108511980929658625'

I get this error:

In an assignment  A(:) = B, the number of elements in A and B must be the
same.

Error in huge_add (line 33)
        zz(ii)=num2str(z(ii));

How can I fix this?

Answer 1

[Srishti Saha]

This works perfectly:

%problem huge add
function summa = huge_add(a,b)
  if ~ischar(a) || ~ischar(b) || sum(isstrprop(a,'digit')) ~= length(a) || ...
          sum(isstrprop(b,'digit')) ~= length(b)
      summa = -1;
      return;
  end
  lng = max([length(a) length(b)]);
  a = [a(end:-1:1) '0'+zeros(1,lng-length(a))];   % flip and pad with zeros if necessary
  b = [b(end:-1:1) '0'+zeros(1,lng-length(b))];   % flip and pad with zeros if necessary
  carry = 0;
  for ii = 1:lng
      c = carry + str2num(a(ii)) + str2num(b(ii)) % add the digits plus the caryy
      carry = c > 9;                              % is there carry? (0 or 1)
      summa(ii) = num2str(mod(c,10));             % put the character in the result
  end
  if carry
      summa(end+1) = '1';                         % need a leading 1 if carry
  end
  summa = summa(end:-1:1);                        % flip it back
end

[Walter Roberson]

We discourage giving complete answers for homework questions.

[Jan]

@Srishti Saha: When a student delivers a solution copied from a forum, this can be treated as trial to cheat. Therefore it is much better to assist the students in finding a solution by their own.

As soon as this forum degrades to a homework cheater community, it will loose its power. Please consider this. Thank you.

Answer 2

[Walter Roberson]

A few lines up from there you have

          zz{ii}=num2str(z(ii));

but in this line you have

          zz(ii)=num2str(z(ii));

Is zz a cell array or is it a numeric array?