from __future__ import division
from math import sqrt
+from operator import attrgetter
import re
-from weakref import proxy
-from cellgroup import Row, Column, Box
+from cell import Cell
+from constraints import Constraint, Row, Column, Box
symbols = [str(x + 1) for x in range(9)] + [chr(x + 97) for x in xrange(26)]
"""
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()
-
class Grid(object):
"""Represents a Sudoku grid."""
def _cellidx(self, row, col):
"""Hashes a row and column into a flat array index."""
- return row * self._size + col
+ return row * self.size + col
@classmethod
def _infer_box_size(cls, dimension):
### Accessors
- def _get_box_height(self):
- return self._box_height
- box_height = property(_get_box_height)
+ def get_constraints(self, constraint_class=Constraint):
+ """Returns constraints of a certain type. Returns all of them by
+ default.
+ """
- def _get_box_width(self):
- return self._box_width
- box_width = property(_get_box_width)
+ condition = lambda constraint: isinstance(constraint, constraint_class)
+ return filter(condition, self._constraints)
- def _get_size(self):
- return self._size
- size = property(_get_size)
+ rows = property(lambda self: self.get_constraints(Row))
+ columns = property(lambda self: self.get_constraints(Column))
+ boxes = property(lambda self: self.get_constraints(Box))
- def _get_cell_groups(self):
- return self._rows + self._columns + self._boxes
- cell_groups = property(_get_cell_groups)
+ box_height = property(attrgetter('_box_height'))
+ box_width = property(attrgetter('_box_width'))
+ size = property(attrgetter('_size'))
+ constraints = property(attrgetter('_constraints'))
### Constructors
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 = 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)
+ self._constraints = []
+ self.add_default_constraints()
+
@classmethod
def from_matrix(cls, rows, box_height=None, box_width=None):
"""Creates and returns a grid read from a list of lists."""
self = cls(box_width=box_width, box_height=box_height)
- for row in xrange(self._size):
- for col in xrange(self._size):
+ 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)
+ self.cell(row, col).set(value - 1, normalize=False)
return self
self = cls(box_width=box_width, box_height=box_height)
- for row in xrange(self._size):
- for col in xrange(self._size):
+ 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))
+ self.cell(row, col).set(symbols.index(ch), normalize=False)
return self
+ ### Constraints
+
+ def add_constraint(self, constraint):
+ self._constraints.append(constraint)
+ for cell in constraint.cells:
+ cell.add_constraint(constraint)
+
+ def add_default_constraints(self):
+ for i in xrange(self.size):
+ self.add_constraint(Row(self, i))
+ self.add_constraint(Column(self, i))
+ self.add_constraint(Box(self, i))
+
+ return
+
### Inspectors
def cell(self, row, column):
return None
+ def normalize_cells(self):
+ """Normalizes every cell in the grid.
+
+ Returns the number of cell changes."""
+
+ cell_changes = 0
+
+ for cell in self._cells:
+ cell_changes += cell.normalize()
+
+ return cell_changes
+
+ def resolve_uniques(self):
+ """Searches each group of cells for a value that can only appear in a
+ single cell.
+
+ Returns the number of cell changes."""
+
+ cell_changes = 0
+
+ for constraint in self.constraints:
+ cell_changes += constraint.resolve_uniques()
+
+ return cell_changes
+
+ _solution_steps = [
+ normalize_cells,
+ resolve_uniques,
+ ]
+
def solve(self):
- """Attempts to solve the grid."""
+ """Attempts to solve the grid by running through various methods of
+ elimination one at a time, from simplest to most complex."""
# 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()
+ while not self.is_filled():
+ cell_changes = 0
- # Step 1: Find values that can only go in one cell in a group
- for group in self.cell_groups:
- group.resolve_uniques()
+ for method in self._solution_steps:
+ cell_changes += method(self)
+ # If we changed something, start over with simple steps again
+ if x != 0:
+ break
- def normalize_cells(self):
- """Normalizes every cell in the grid."""
- for cell in self._cells:
- cell.normalize()
+ # If we didn't do anything this round, we're stuck
+ if cell_changes == 0:
+ break
projects / pseudoku.git / blobdiff