kkck: A solver for Kriss Kross puzzles

# - - -   P u z z l e . _ _ r e d u c e C y c l e

    def __reduceCycle ( self ):
        '''One cycle of cyclic reduction.

          [ self.__wordBank  :=  self.__wordBank - (choices
                eliminated at slot intersections, if any) ]
        '''

This method performs the three types of static reduction in word choices described in Section 4.5, “Cyclic reduction”.

First, we visit every cell in the puzzle (using Section 33, “Puzzle.genCells(): Generate all the cells”), but we are interested only in those cells that are related to two slots. For each such cell, we try to eliminate any choices from the intersecting slots. For the process carried out for each pair, see Section 40, “Puzzle.__reduceCell(): Eliminate choices where two slots intersect”.

        #-- 1 --
        if VERBOSE: print "=== Reduction cycle"
        for cell in self.genCells():
            #-- 1 body --
            # [ if cell is related to two slots ->
            #       self.__wordBank  :=  self.__wordBank -
            #           (choices for those slots that have letters at
            #           cell's position not found in the intersecting
            #           slot)
            #   else -> I ]
            self.__reduceCell ( cell )

Next, we perform the unique word test for all slots.

        #-- 2 --
        for slot in self.__slotMap.values():
            #-- 2 body --
            # [ if slot has only one choice ->
            #     remove that choice from all other slots
            #   else -> I ]
            self.__uniqueWordTest ( slot )

Finally, we perform the unique slot test for all words.

        #-- 3 --
        for word in self.__wordBank.genAllWords():
            #-- 3 body --
            # [ if word occurs in only one slot's choices ->
            #      self.__wordBank  :=  self.__wordBank - (choices
            #          for slot other than word) - (choices for
            #          that word in all slots)
            #   else -> I ]
            self.__uniqueSlotTest ( word )