I am trying to write a matlab code to check a solved 9X9 sudoku problem. I can't seem to get it to work. Any ideas where I went wrong?

function valid = sudoku (m)
valid = (size(m) == [9, 9]);
if (~valid)
  fprintf('Sudoku: size must be 9x9\n');
  return;
end;

valid = ((min(min(m)) >= 0) && (max(max(m)) <= 9));
if (~valid)
  fprintf(['Sudoku: ', ...
          'all entries must be integers between 0 and 9\n']);
  return;
end;

% 1. check rows
for row = 1:9,
  count = zeros(1, 9);
  for col = 1:9,
    data = m(row, col);
    if (data > 0)
      count(data) = count(data)+1;
    end;
  end;
  valid = (max(count) <= 1);
  if (~valid)
    fprintf('Sudoku: row %i looks bad\n', row);
    return;
  end;  
end;

% 2. check columns
for col = 1:9,
  count = zeros(1, 9);
  for row = 1:9,
    data = m(row, col);
    if (data > 0)
      count(data) = count(data)+1;
    end;
  end;
  valid = (max(count) <= 1);
  if (~valid)
    fprintf('Sudoku: col %i looks bad\n', col);
    return;
  end;  
end;

% 3. check subsquares
for k = 0:8,
  count = zeros(1, 9);
  rowBase = 3*floor(k/3);
  colBase = 3*mod(k,3);
  for col = colBase+(1:3),
    for row = rowBase+(1:3),
      data  = m(row, col);
      if (data > 0)
        count(data) = count(data)+1;
      end;
    end;
  end;

    valid = (max(count) <= 1);
    if (~valid)
      fprintf('Sudoku: subsquare %i looks bad\n', k+1);
      return;
    end;  
  end;

 return;

[dpb]

The following jumped out at me altho it's a nit and probably the rarest of cases--

"fprintf(['Sudoku: ', ... 'all entries must be integers between 0 and 9\n']);"

...
'all entries must be integers between 1 and 9, inclusive\n']);

Answer 1

[MHN]

It works fine !

m = randi(9,9,9);

valid = (size(m) == [9, 9]);
if (~valid)
  fprintf('Sudoku: size must be 9x9\n');
  return;
end;

valid = ((min(min(m)) >= 1) && (max(max(m)) <= 9));
if (~valid)
  fprintf(['Sudoku: ', ...
          'all entries must be integers between 1 and 9\n']);
  return;
end;

% 1. check rows
for row = 1:9,
  count = zeros(1, 9);
  for col = 1:9,
    data = m(row, col);
    if (data > 0)
      count(data) = count(data)+1;
    end;
  end;
  valid = (max(count) <= 1);
  if (~valid)
    fprintf('Sudoku: row %i looks bad\n', row);
    return;
  end;  
end;

% 2. check columns
for col = 1:9,
  count = zeros(1, 9);
  for row = 1:9,
    data = m(row, col);
    if (data > 0)
      count(data) = count(data)+1;
    end;
  end;
  valid = (max(count) <= 1);
  if (~valid)
    fprintf('Sudoku: col %i looks bad\n', col);
    return;
  end;  
end;

% 3. check subsquares
for k = 0:8,
  count = zeros(1, 9);
  rowBase = 3*floor(k/3);
  colBase = 3*mod(k,3);
  for col = colBase+(1:3),
    for row = rowBase+(1:3),
      data  = m(row, col);
      if (data > 0)
        count(data) = count(data)+1;
      end;
    end;
  end;

      valid = (max(count) <= 1);
      if (~valid)
        fprintf('Sudoku: subsquare %i looks bad\n', k+1);
        return;
      end;  
    end;