# - - - P u z z l e . _ _ g e n C l u m p s def __genClumps ( self, j, isV ): '''Generate multi-cell clumps in a row or column. [ (isV is 0 for horizontal, 1 for vertical) and (j is a valid row or column index for that orientation) -> generate (start, length) tuples for all contiguous groups of two or more cells in that orientation from self.__cellMap ] '''
For example, consider this nine-element row in the framework section:
### # ###
There are two slots here. One starts at column 0 for a length of 3; the other starts at column 6 for a length of 3. The cell at column 4 is not part of a horizontal slot.
So our problem is to detect transitions between elements without cells and elements with cells, and then count the sequence of contiguous cells after each transition, and if the sequence is length 2 or greater, we'll call it a slot.
We'll use a simple state machine here. Variable
start is initially set to
it is set back to
None every time we see an
element without a cell. Then, as we step through the
elements, we'll set
start to the element
index whenever it changes from no cell to cell. When we
see a transition from cell to no cell, if
start is not
None, then a slot
exists starting at
start and extending
through the previous position in our scan.
There is one edge case we need to eliminate. If there is a cell at the last position, we will not see the cell→no-cell transition. To eliminate this special case, we will build a list containing 0's where there are no cells and 1's where there are cells, and then append one extra zero so there will always be a cell→no-cell transition even if the last element contains a cell.
First, build the list of 0's and 1's. Cells are detected
by calling Section 32, “
Puzzle.whatCell(): Is there a cell at a
given coordinate?”. Then we
run our little state machine and generate the
#-- 1 -- # [ mask := a list containing 1s where row or column j # has cells, 0s where it has no cells, with one # extra 0 appended ] mask = [ self.whatCell ( coord ) is not None for coord in self.scan ( j, isV ) ] mask.append ( 0 ) #-- 2 -- # [ generate (start, length) tuples for consecutive # groups of two or more 1s in mask ] start = None for i in range(len(mask)): if mask[i]: if start is None: start = i else: if start is not None: if (i-start) > 1: yield (start, i-start) start = None #-- 3 -- raise StopIteration