115 lines
3.5 KiB
Python
115 lines
3.5 KiB
Python
#!env python3
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# Eryn Wells <eryn@erynwells.me>
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'''
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A Sudoku puzzle solver.
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'''
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import itertools
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import math
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class Sudoku:
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def __init__(self, size=9, board=None):
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dim = math.sqrt(size)
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if dim != int(dim):
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raise ValueError('Board size must have an integral square root.')
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self._dimension = int(dim)
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self.size = size
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if board:
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self._board = bytearray(board)[:size**2]
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else:
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self._board = bytearray(b'\x00' * (size * size))
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@property
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def dimension(self):
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return self._dimension
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@property
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def rows(self):
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return self._apply_index_ranges(self.index_rows)
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@property
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def columns(self):
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return self._apply_index_ranges(self.index_columns)
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@property
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def squares(self):
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return self._apply_index_ranges(self.index_squares)
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@property
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def index_rows(self):
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'''
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Return an iterable of ranges of indexes into the board, each defining a row.
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'''
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sz = self.size
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return (self._row(i, size) for i in range(sz))
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@property
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def index_columns(self):
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'''
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Return an iterable of ranges of indexes into the board, each defining a column.
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'''
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sz = self.size
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sz2 = sz ** 2
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return (self._column(c, sz, sz2) for i in range(sz))
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@property
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def index_squares(self):
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'''
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Return an iterable of ranges of indexes into the board, each defining a square.
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'''
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dim = self.dimension
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return (self._square(x, y, dim) for y in range(dim) for x in range(dim))
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# TODO: Break the above into helper methods that produce a single thing given an index.
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def _row(self, r, size):
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return range(r * size, r * size + size)
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def _column(self, c, size, size2):
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return range(c, size2, size)
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def _square(self, x, y, dim):
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if (x < 0 or x >= dim) or (y < 0 or y >= dim):
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raise IndexError('Invalid coordinates for square: ({}, {})'.format(x, y))
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offset = (x * dim, y * dim * self.size)
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def _range(i):
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start = (offset[1] + i * self.size) + offset[0]
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return range(start, start + dim)
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ranges = itertools.chain(*[_range(i) for i in range(dim)])
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return ranges
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@property
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def solved(self):
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expected = set(range(self.size))
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return all([
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all(expected == set(row) for row in self.rows),
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all(expected == set(col) for col in self.columns),
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all(expected == set(sqr) for sqr in self.squares)
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])
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def _apply_index_ranges(self, ranges):
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return ((self._board[i] for i in r) for r in ranges)
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def __str__(self):
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field_width = len(str(self.size))
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dim = self.dimension
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lines = []
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spacer = '{0}{1}{0}'.format('+', '+'.join(['-' * (field_width * dim) for _ in range(dim)]))
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for line in range(self.size):
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chunks = []
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for i in range(dim):
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fields = []
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for j in range(dim):
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idx = line * self.size + i * dim + j
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fields.append('{{board[{i}]:^{width}}}'.format(i=idx, width=field_width))
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chunks.append(''.join(fields))
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if (line % dim) == 0:
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lines.append(spacer)
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lines.append('{0}{1}{0}'.format('|', '|'.join(chunks)))
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lines.append(spacer)
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fmt = '\n'.join(lines)
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str_board = [str(n) if n != 0 else ' ' for n in self._board]
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out = fmt.format(board=str_board)
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return out
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