X-Git-Url: http://git.veekun.com/pseudoku.git/blobdiff_plain/282da8de86748e42e0891daaa7ce81aa423fed44..bfc07962deafde17e2b41f8d659313b7746dca07:/lib/pseudoku/grid/__init__.py

diff --git a/lib/pseudoku/grid/__init__.py b/lib/pseudoku/grid/__init__.py
new file mode 100644
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+++ b/lib/pseudoku/grid/__init__.py
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+from __future__ import division
+
+from math import sqrt
+import re
+from weakref import proxy
+
+from cellgroup import Row, Column, Box
+
+symbols = [str(x + 1) for x in range(9)] + [chr(x + 97) for x in xrange(26)]
+
+class GridSizeError(Exception):
+    pass
+
+class Cell(object):
+    """Represents a single cell/value within a sudoku grid."""
+
+    ### Accessors
+
+    def _get_solved(self):
+        """True iff this cell has been solved."""
+        return len(self._values) == 1
+    solved = property(_get_solved)
+
+    def _get_value(self):
+        """Returns this cell's value, if it has one known."""
+        if self.solved:
+            return self._values[0]
+        return None
+    value = property(_get_value)
+
+    def _get_row(self):
+        """Returns the Row object associated with this cell."""
+        return self._grid._rows[self._row]
+    row = property(_get_row)
+
+    def _get_column(self):
+        """Returns the Column object associated with this cell."""
+        return self._grid._columns[self._col]
+    column = property(_get_column)
+
+    def _get_box(self):
+        """Returns the Box object associated with this cell."""
+        # Some actual math required here!
+        # Row 0..2 -> box 0..2
+        # Col 0..2 -> box 0, 3, 6 (box col 0)
+        box_row = self._row // self._grid._box_height
+        box_col = self._col // self._grid._box_width
+        box_idx = box_row * self._grid._box_height + box_col
+        return self._grid._boxes[box_idx]
+    box = property(_get_box)
+
+    def __init__(self, grid, row, column):
+        self._grid = proxy(grid)
+        self._row = row
+        self._col = column
+        self._values = range(self._grid.size)
+        self._normalized = False
+
+    def set_naively(self, value):
+        """Sets the value of this cell, WITHOUT eliminating the value from
+        every other cell in its row/column/box.
+        """
+
+        self._values = [value]
+
+    def set(self, value):
+        """Sets the value of this cell and adjusts the grid accordingly."""
+        self.set_naively(value)
+        self._normalized = False
+        self.normalize()
+
+
+
+    def normalize(self):
+        """Checks to see if this cell has only one possible value left.  If
+        so, sets that as its value and eliminates it from every related cell.
+        This method is exhaustive; that repeated calls should have no effect.
+        """
+
+        if self._normalized:
+            # Already done
+            return
+
+        # Set this now just in case of infinite looping
+        self._normalized = True
+
+        if not self.solved:
+            # Don't know the value yet
+            return
+
+        # Elimination time
+        for group_type in 'row', 'column', 'box':
+            group = getattr(self, group_type)
+            for cell in group.cells:
+                if cell == self:
+                    continue
+                cell.eliminate(self.value)
+
+
+    def eliminate(self, value):
+        """Eliminates the given value as a possibility for this cell."""
+        if value in self._values:
+            self._values.remove(value)
+
+            if len(self._values) == 0:
+                # XXX give me a real exception here
+                raise Exception
+
+            self._normalized = False
+            self.normalize()
+
+
+    def __str__(self):
+        """Stringification for pretty-printing."""
+        if self.value != None:
+            return symbols[self.value]
+
+        return '.'
+
+
+class Grid(object):
+    """Represents a Sudoku grid."""
+
+    ### Utilities
+
+    def _cellidx(self, row, col):
+        """Hashes a row and column into a flat array index."""
+        return row * self._size + col
+
+    @classmethod
+    def _infer_box_size(cls, dimension):
+        """Attempts to infer the size of a box, given some dimension of the
+        entire grid, i.e. the number of cells per box/row/column.
+        
+        Returns a tuple of height, width."""
+        
+        # Most obvious: probably n * n.
+        root = int(sqrt(dimension))
+        if root ** 2 == dimension:
+            return root, root
+
+        # Otherwise, probably n * (n - 1) or n * (n - 2).
+        # These puzzles generally have the wide side (n) as the width.
+        # This is of course entirely unreliable, but better than nothing..
+        #   n^2 - (1|2)n - dimension = 0
+        #   Determinant is (1|2)^2 + 4 * dimension and has to be square
+        for difference in 1, 2:
+            determinant = difference ** 2 + 4 * dimension
+            root = int(sqrt(determinant))
+            if root ** 2 != determinant:
+                continue
+
+            n = (-difference + root) / 2
+            if n != int(n):
+                continue
+
+            # Success!
+            return n - difference, n
+        
+        # Okay, I don't have a clue.
+        raise GridSizeError("Can't infer box height and width for grid size "
+                            "%d; please specify them manually" % dimension)
+
+    ### Accessors
+
+    def _get_box_height(self):
+        return self._box_height
+    box_height = property(_get_box_height)
+
+    def _get_box_width(self):
+        return self._box_width
+    box_width = property(_get_box_width)
+
+    def _get_size(self):
+        return self._size
+    size = property(_get_size)
+
+    def _get_cell_groups(self):
+        return self._rows + self._columns + self._boxes
+    cell_groups = property(_get_cell_groups)
+
+    ### Constructors
+
+    def __init__(self, box_height=3, box_width=None):
+        if not box_width:
+            box_width = box_height
+
+        self._box_height = box_height
+        self._box_width = box_width
+        self._size = box_height * box_width
+
+        self._rows = [Row(self, i) for i in xrange(self._size)]
+        self._columns = [Column(self, i) for i in xrange(self._size)]
+        self._boxes = [Box(self, i) for i in xrange(self._size)]
+
+        self._cells = range(self._size ** 2)
+        for row in xrange(self._size):
+            for col in xrange(self._size):
+                self._cells[self._cellidx(row, col)] \
+                    = Cell(self, row, col)
+
+    @classmethod
+    def from_matrix(cls, rows, box_height=None, box_width=None):
+        """Creates and returns a grid read from a list of lists."""
+
+        if not box_height:
+            box_height, box_width = cls._infer_box_size(len(rows))
+        elif not box_width:
+            box_width = box_height
+
+        self = cls(box_width=box_width, box_height=box_height)
+
+        for row in xrange(self._size):
+            for col in xrange(self._size):
+                value = rows[row][col]
+                if not value:
+                    continue
+                self.cell(row, col).set_naively(value - 1)
+
+        return self
+
+    @classmethod
+    def from_string(cls, grid, box_height=None, box_width=None):
+        # XXX sanity check dimensions
+        """Creates and returns a grid from a string of symbols.
+
+        Symbols are the digits 1 to 9 followed by the letters of the alphabet.
+        Zeroes and periods are assumed to be empty cells.  All other characters
+        are ignored.
+
+        Since whitespace is ignored, the string could be all in one line or
+        laid out visually in a square, one row per line."""
+
+        # Collapse the string down to just characters we want
+        grid = grid.lower()
+        grid = re.sub('\\.', '0', grid)
+        grid = re.sub('[^0-9a-z]', '', grid)
+
+        # Figure out the length of one side/box
+        size = int(sqrt(len(grid)))
+        if size ** 2 != len(grid):
+            raise GridSizeError("Provided string does not form a square")
+
+        # Set height/width..
+        if not box_height:
+            box_height, box_width = cls._infer_box_size(size)
+        elif not box_width:
+            box_width = box_height
+
+        self = cls(box_width=box_width, box_height=box_height)
+
+        for row in xrange(self._size):
+            for col in xrange(self._size):
+                ch = grid[ self._cellidx(row, col) ]
+                if ch == '0':
+                    continue
+                self.cell(row, col).set_naively(symbols.index(ch))
+
+        return self
+
+    ### Methods
+
+    def cell(self, row, column):
+        return self._cells[self._cellidx(row, column)]
+
+
+    ### Solving
+
+    def check(self):
+        """Returns True iff the grid is solved.  Raises an exception if an
+        integrity problem is found, such as a value appearing twice in a row.
+        """
+        # TODO
+        return None
+
+    def solve(self):
+        """Attempts to solve the grid."""
+        # XXX track how many cells are changed and repeat as appropriate
+
+        # Step 0: Normalize cells, i.e. find any that can only be one value
+        self.normalize_cells()
+
+        # Step 1: Find values that can only go in one cell in a group
+        for group in self.cell_groups:
+            group.resolve_uniques()
+
+
+    def normalize_cells(self):
+        """Normalizes every cell in the grid."""
+        for cell in self._cells:
+            cell.normalize()
+
+
+    def __str__(self):
+        """Pretty-printing."""
+        divider = '+'
+        for box in xrange(self._box_height):
+            for col in xrange(self._box_width):
+                divider += '-'
+            divider += '+'
+
+        res = ''
+        for row in xrange(self._size):
+            if row % self._box_height == 0:
+                res += divider
+                res += "\n"
+
+            for col in xrange(self._size):
+                if col % self._box_width == 0:
+                    res += '|'
+                res += str(self.cell(row, col))
+
+            res += '|'
+            res += "\n"
+
+        res += divider
+        res += "\n"
+
+        return res