From c120ddc4fa472b2430a431695e3ef58e12cb223b Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Wed, 28 Aug 2013 23:09:55 -0700
Subject: [PATCH 01/22] Add sudoku module -- work thus far

---
 sudoku.py | 166 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 166 insertions(+)
 create mode 100644 sudoku.py

diff --git a/sudoku.py b/sudoku.py
new file mode 100644
index 0000000..5540925
--- /dev/null
+++ b/sudoku.py
@@ -0,0 +1,166 @@
+#!/usr/bin/env python3
+# Eryn Wells <eryn@erynwells.me>
+
+'''
+A Sudoku solver.
+'''
+
+import logging
+import math
+
+LOG = logging.getLogger(__name__)
+
+
+class Board(dict):
+    def __init__(self, size=9, **kwargs):
+        self.size = size
+
+        # Verify size is a perfect square. The sqrt(size) is also the dimension of each box on the
+        # Sudoku grid.
+        self.box_size = int(math.sqrt(size))
+        assert self.box_size == int(self.box_size), 'Invalid size; value must be a perfect square'
+
+        # The range of possible values for a square.
+        possible_values = range(1, self.size + 1)
+
+        def kwget(x, y):
+            '''
+            Try to get an initial value for square ({x}, {y}) from the given kwargs. If none exists, return a list of
+            all possible values for the square. If an initial value was given, make sure it is one of the valid initial
+            values. Raise a ValueError if not.
+            '''
+            initial_value = kwargs.get('x{}y{}'.format(x, y))
+            if initial_value is None:
+                return list(possible_values)
+            if initial_value not in possible_values:
+                raise ValueError('Invalid initial value for square ({}, {}): {}'.format(x, y, initial_value))
+            return [initial_value]
+
+        # Make the grid.
+        super(Board, self).__init__([(self._xy_key(x, y), kwget(x, y))
+                                     for x in range(self.size)
+                                     for y in range(self.size)])
+
+    def _xy_key(self, x, y):
+        '''
+        Given {x} and {y}, generate a key to refer to the square at coordinate (x, y) in the grid.
+        '''
+        return (int(x), int(y))
+
+    def row(self, idx):
+        '''
+        Return a dict of all squares in the {idx}'th row.
+        '''
+        assert idx >= 0 and idx < self.size, 'Invalid row index; value must be >= 0 and < {}'.format(self.size)
+        # key[1] is Y coordinate in the grid.
+        return {k: v for k, v in self.items() if k[1] == idx}
+
+    def col(self, idx):
+        '''
+        Return a dict of all squares in the {idx}'th column.
+        '''
+        assert idx >= 0 and idx < self.size, 'Invalid column index; value must be >= 0 and < {}'.format(self.size)
+        # key[0] is X coordinate in the grid.
+        return {k: v for k, v in self.items() if k[0] == idx}
+
+    def box(self, x, y):
+        '''
+        Given a square at coordinates ({x}, {y}), return a dictionary containing the squares that make up the box that
+        contains the point.
+        '''
+        bx = int(x / self.box_size) * self.box_size
+        by = int(y / self.box_size) * self.box_size
+        bx_range = range(bx, bx + self.box_size)
+        by_range = range(by, by + self.box_size)
+        return {k: v for k, v in self.items() if k[0] in bx_range and k[1] in by_range}
+
+    def peers(self, x, y):
+        # Generate a dictionary of all the squares in the row, column, and box containing the given square.
+        peers = dict(list(self.row(y).items()) + list(self.col(x).items()) + list(self.box(x, y).items()))
+        # Remove the given square.
+        del peers[self._xy_key(x, y)]
+        return peers
+
+    def clear(self):
+        '''
+        Clear the board.
+        '''
+        for square in self:
+            self[square] = list(range(1, self.size + 1))
+
+    def eliminate(self, square, value):
+        '''
+        Eliminate {value} from square at ({x}, {y}).
+        '''
+        if value not in self[square]:
+            LOG.debug('Value {} not in square {}; skipping'.format(value, square))
+            return
+
+        # Update peer value list.
+        super(Board, self).__setitem__(square, [v for v in self[square] if v != value])
+        LOG.debug('Eliminating {} from square {}'.format(value, square))
+
+        # (1) If a square is reduced to one value, eliminate that value from its peers.
+        if len(self[square]) == 0:
+            # Whoops. Removed the last value... We have a contradiction now.
+            LOG.error('Removed last value from square {}'.format(square))
+            raise ValueError('Removed last value from square {}; board is now invalid'.format(square))
+        elif len(self[square]) == 1:
+            # One value left in this square. Propagate changes to its peers.
+            LOG.debug('One value left in square {}; eliminating {} from its peers'.format(square, self[square][0]))
+            try:
+                for peer in self.peers(*square):
+                    self.eliminate(peer, self[square][0])
+            except ValueError:
+                raise
+
+        # (2) If a unit has only one square for a value, put it there.
+        for unit in (self.row(square[1]), self.col(square[0]), self.box(*square)):
+            places = [sq for sq in unit if value in unit[sq]]
+            if len(places) == 0:
+                LOG.error('No place for value {} to go in unit {}'.format(value, unit))
+                raise ValueError('No place for value {} to go in unit {}; board is now invalid'.format(value, unit))
+            elif len(places) == 1:
+                LOG.debug('One place for value {} to be in unit {}; setting'.format(value, unit))
+                self[places[0]] = [value]
+        return True
+
+    def __delitem__(self, key):
+        # Don't allow deleting keys from self.
+        pass
+
+    def __setitem__(self, key, value):
+        #if key not in self:
+            # Don't allow adding new keys, only changes to existing ones.
+            #return
+        LOG.debug('Setting value {} at {}.'.format(value, key))
+        removed_values = set(self[key]) - set(value)
+        for v in removed_values:
+            self.eliminate(key, v)
+
+    def __str__(self):
+        lines = []
+        box_lines = []
+        for x in range(self.size):
+            row_squares = []
+            box_squares = []
+            for y in range(self.size):
+                square = self.get(self._xy_key(x, y))
+                if len(square) == 1:
+                    box_squares.append(str(square[0]))
+                else:
+                    box_squares.append('.')
+                if len(box_squares) == self.box_size:
+                    row_squares.append(' '.join(box_squares))
+                    box_squares = []
+            # Print a divider between boxes.
+            box_lines.append(' | '.join(row_squares))
+            if len(box_lines) == self.box_size:
+                lines.append('\n'.join(box_lines))
+                box_lines = []
+                if x < self.size - 1:
+                    box_dividers = ['-' * (2 * self.box_size - 1) for box in range(self.box_size)]
+                    lines.append('\n{}\n'.format('-+-'.join(box_dividers)))
+        return ''.join(lines)
+
+

From af92bb89f82591359be1ec6d97fac10aa465aed4 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Wed, 28 Aug 2013 23:10:15 -0700
Subject: [PATCH 02/22] Ignore *.pyc

---
 .gitignore | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 .gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..0d20b64
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.pyc

From 31415f81754b466055161927372562aeeacb3f4b Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Wed, 28 Aug 2013 23:10:27 -0700
Subject: [PATCH 03/22] Ignore __pycache__/

---
 .gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.gitignore b/.gitignore
index 0d20b64..d646835 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 *.pyc
+__pycache__/

From 7fd051802c0719dfb56c240e3bd59404eda6035e Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 09:42:06 -0700
Subject: [PATCH 04/22] Implement the solved property

---
 sudoku.py | 42 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 6 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index 5540925..e810099 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -21,7 +21,7 @@ class Board(dict):
         assert self.box_size == int(self.box_size), 'Invalid size; value must be a perfect square'
 
         # The range of possible values for a square.
-        possible_values = range(1, self.size + 1)
+        self.possible_values = range(1, self.size + 1)
 
         def kwget(x, y):
             '''
@@ -31,8 +31,8 @@ class Board(dict):
             '''
             initial_value = kwargs.get('x{}y{}'.format(x, y))
             if initial_value is None:
-                return list(possible_values)
-            if initial_value not in possible_values:
+                return list(self.possible_values)
+            if initial_value not in self.possible_values:
                 raise ValueError('Invalid initial value for square ({}, {}): {}'.format(x, y, initial_value))
             return [initial_value]
 
@@ -42,11 +42,41 @@ class Board(dict):
                                      for y in range(self.size)])
 
     def _xy_key(self, x, y):
-        '''
-        Given {x} and {y}, generate a key to refer to the square at coordinate (x, y) in the grid.
-        '''
+        '''Given {x} and {y}, generate a key to refer to the square at coordinate (x, y) in the grid.'''
         return (int(x), int(y))
 
+    @property
+    def solved(self):
+        '''
+        Determines if the board has been solved. First, determine if all squares have no more than one value (i.e. they
+        have had values assigned to them). If not, return False. If so, check each unit (rows, columns, and boxes) to
+        make sure that each has one and only one of each value in the range of possible values for a unit. If not,
+        return False; otherwise, return True.
+        '''
+        if not all(len(s) == 1 for s in self.values()):
+            return False
+
+        def validate_unit(unit):
+            '''
+            Validate {unit} by ensuring it has exactly 1 of each value in the range of possible values.
+            '''
+            necessary_values = list(self.possible_values)
+            for square, values in unit.items():
+                v = values[0]
+                if v in necessary_values:
+                    necessary_values.remove(v)
+                else:
+                    return False
+            if len(necessary_values) != 0:
+                return False
+            return True
+
+        return (    all(validate_unit(self.row(r)) for r in range(self.size))
+                and all(validate_unit(self.col(c)) for c in range(self.size))
+                and all(validate_unit(self.box(x, y))
+                        for x in range(0, self.size, self.box_size)
+                        for y in range(0, self.size, self.box_size)))
+
     def row(self, idx):
         '''
         Return a dict of all squares in the {idx}'th row.

From 6a753a8dacc27ed0fcb566531242b1f69cf64fa3 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 09:52:52 -0700
Subject: [PATCH 05/22] Docstring updates

---
 sudoku.py | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index e810099..0eb3b34 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -105,6 +105,10 @@ class Board(dict):
         return {k: v for k, v in self.items() if k[0] in bx_range and k[1] in by_range}
 
     def peers(self, x, y):
+        '''
+        Generate and return a list of peers for the square at coordinates ({x}, {y}). Peers are defined as all the
+        squares in the same row, column, and box as the given square.
+        '''
         # Generate a dictionary of all the squares in the row, column, and box containing the given square.
         peers = dict(list(self.row(y).items()) + list(self.col(x).items()) + list(self.box(x, y).items()))
         # Remove the given square.
@@ -113,14 +117,17 @@ class Board(dict):
 
     def clear(self):
         '''
-        Clear the board.
+        Clear the board. Resets each square's possible value list to the full range of possible values for this board.
         '''
         for square in self:
             self[square] = list(range(1, self.size + 1))
 
     def eliminate(self, square, value):
         '''
-        Eliminate {value} from square at ({x}, {y}).
+        Eliminate {value} from {square}, propagating changes to the squares peers as necessary. This process involves
+        two logical rules of Sudoku. First, if a square is reduced to a single possible value, assign that value to the
+        square and remove the value from the possible value lists of its peers. Second, if a unit has only one square
+        that can hold a value, put the value in that square and propagate that change to its peers.
         '''
         if value not in self[square]:
             LOG.debug('Value {} not in square {}; skipping'.format(value, square))
@@ -160,9 +167,15 @@ class Board(dict):
         pass
 
     def __setitem__(self, key, value):
-        #if key not in self:
+        '''
+        Set the square defined by {key}'s value to {value}. {value} is expected to be an iterable (a list). {key} should
+        be a valid (x, y) coordinate pair for referencing a square on the board.
+        '''
+        if key not in self:
             # Don't allow adding new keys, only changes to existing ones.
-            #return
+            raise KeyError('Key {} is not a valid coordinate pair.'.format(key))
+
+        # Remove all values other than the one given from the square.
         LOG.debug('Setting value {} at {}.'.format(value, key))
         removed_values = set(self[key]) - set(value)
         for v in removed_values:

From 8540f60381042265dc883e9e5e9f5efdbbb04586 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 11:49:34 -0700
Subject: [PATCH 06/22] Use length of str(self.size) to compute size of each
 square in the printed grid

---
 sudoku.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index 0eb3b34..6c4ec6c 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -184,15 +184,16 @@ class Board(dict):
     def __str__(self):
         lines = []
         box_lines = []
+        square_size = len(str(self.size))
         for x in range(self.size):
             row_squares = []
             box_squares = []
             for y in range(self.size):
                 square = self.get(self._xy_key(x, y))
                 if len(square) == 1:
-                    box_squares.append(str(square[0]))
+                    box_squares.append(str(square[0]).center(square_size))
                 else:
-                    box_squares.append('.')
+                    box_squares.append('.'.center(square_size))
                 if len(box_squares) == self.box_size:
                     row_squares.append(' '.join(box_squares))
                     box_squares = []
@@ -202,7 +203,7 @@ class Board(dict):
                 lines.append('\n'.join(box_lines))
                 box_lines = []
                 if x < self.size - 1:
-                    box_dividers = ['-' * (2 * self.box_size - 1) for box in range(self.box_size)]
+                    box_dividers = ['-' * (square_size * (2 * self.box_size - 1)) for box in range(self.box_size)]
                     lines.append('\n{}\n'.format('-+-'.join(box_dividers)))
         return ''.join(lines)
 

From cac812e46f2c0c097199f87a95fc0a7d5e60dd9d Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 11:57:31 -0700
Subject: [PATCH 07/22] Fix divider length computation

---
 sudoku.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sudoku.py b/sudoku.py
index 6c4ec6c..4376269 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -203,7 +203,7 @@ class Board(dict):
                 lines.append('\n'.join(box_lines))
                 box_lines = []
                 if x < self.size - 1:
-                    box_dividers = ['-' * (square_size * (2 * self.box_size - 1)) for box in range(self.box_size)]
+                    box_dividers = ['-' * (square_size * self.box_size + square_size)) for box in range(self.box_size)]
                     lines.append('\n{}\n'.format('-+-'.join(box_dividers)))
         return ''.join(lines)
 

From d20a0bbdf74a2dea0601c5de116b93be9efaaa80 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@vmware.com>
Date: Thu, 29 Aug 2013 12:05:34 -0700
Subject: [PATCH 08/22] Fix the divider printing logic (again)

---
 sudoku.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sudoku.py b/sudoku.py
index 4376269..5dfd47d 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -203,7 +203,8 @@ class Board(dict):
                 lines.append('\n'.join(box_lines))
                 box_lines = []
                 if x < self.size - 1:
-                    box_dividers = ['-' * (square_size * self.box_size + square_size)) for box in range(self.box_size)]
+                    # Don't print a divider on the last line.
+                    box_dividers = ['-' * ((square_size + 1) * self.box_size - 1) for box in range(self.box_size)]
                     lines.append('\n{}\n'.format('-+-'.join(box_dividers)))
         return ''.join(lines)
 

From a926bc5a99e0d69a485897ea70b50d5e9e636fca Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@vmware.com>
Date: Thu, 29 Aug 2013 15:05:30 -0700
Subject: [PATCH 09/22] Board.solve() and Board.assign()

---
 sudoku.py | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index 5dfd47d..9da9aa5 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -122,6 +122,29 @@ class Board(dict):
         for square in self:
             self[square] = list(range(1, self.size + 1))
 
+    def solve(self):
+        for square, values in self.items():
+            if len(values) == 1:
+                try:
+                    self.assign(square, values)
+                except ValueError:
+                    raise
+        return self.solved
+
+    def assign(self, square, value):
+        '''
+        Assign {value} to {square}. {value} is expected to be an iterable (a list). {key} should be a valid (x, y)
+        coordinate pair for referencing a square on the board.
+        '''
+        LOG.debug('Assigning values {} to square {}.'.format(value, square))
+        removed_values = set(self[square]) - set(value)
+        for v in removed_values:
+            try:
+                self.eliminate(square, v)
+            except ValueError:
+                raise
+        return True
+
     def eliminate(self, square, value):
         '''
         Eliminate {value} from {square}, propagating changes to the squares peers as necessary. This process involves
@@ -131,7 +154,7 @@ class Board(dict):
         '''
         if value not in self[square]:
             LOG.debug('Value {} not in square {}; skipping'.format(value, square))
-            return
+            return True
 
         # Update peer value list.
         super(Board, self).__setitem__(square, [v for v in self[square] if v != value])
@@ -167,19 +190,10 @@ class Board(dict):
         pass
 
     def __setitem__(self, key, value):
-        '''
-        Set the square defined by {key}'s value to {value}. {value} is expected to be an iterable (a list). {key} should
-        be a valid (x, y) coordinate pair for referencing a square on the board.
-        '''
         if key not in self:
             # Don't allow adding new keys, only changes to existing ones.
             raise KeyError('Key {} is not a valid coordinate pair.'.format(key))
-
-        # Remove all values other than the one given from the square.
-        LOG.debug('Setting value {} at {}.'.format(value, key))
-        removed_values = set(self[key]) - set(value)
-        for v in removed_values:
-            self.eliminate(key, v)
+        self.assign(key, value)
 
     def __str__(self):
         lines = []

From 3c21549ee93d89b5b0c626249b3fa28a863459ac Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@vmware.com>
Date: Thu, 29 Aug 2013 15:05:38 -0700
Subject: [PATCH 10/22] Bare bones tests module

---
 tests.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 tests.py

diff --git a/tests.py b/tests.py
new file mode 100644
index 0000000..cd64084
--- /dev/null
+++ b/tests.py
@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# Eryn Wells <eryn@erynwells.me>
+
+'''
+Tests for sudoku.
+'''
+
+import nose
+import sudoku
+import unittest
+
+
+def main():
+    nose.main()
+
+
+if __name__ == '__main__':
+    main()

From 7e43451eb5037a1bfdec1b1272c23b71cfa19831 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@vmware.com>
Date: Thu, 29 Aug 2013 15:58:43 -0700
Subject: [PATCH 11/22] Tests yay!

---
 tests.py | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/tests.py b/tests.py
index cd64084..d413bb1 100644
--- a/tests.py
+++ b/tests.py
@@ -10,6 +10,97 @@ import sudoku
 import unittest
 
 
+def test_9x9_dimensions():
+    '''
+    Test dimenions of a 9x9 Sudoku board.
+    '''
+    b = sudoku.Board()
+    assert len(b.keys()) == 81
+    assert b.size == 9
+    assert b.box_size == 3
+    for square, values in b.items():
+        assert len(values) == 9
+
+
+def test_9x9_units():
+    '''
+    Test units of a 9x9 Sudoku board.
+    '''
+    b = sudoku.Board()
+    for r in range(b.size):
+        row = b.row(r)
+        assert len(row) == 9
+        for sq in row:
+            assert sq[1] == r
+
+    for c in range(b.size):
+        col = b.col(c)
+        assert len(col) == 9
+        for sq in col:
+            assert sq[0] == c
+
+    for x in range(0, b.size, b.box_size):
+        for y in range(0, b.size, b.box_size):
+            box = b.box(x, y)
+            assert len(box) == 9
+            # TODO: Finish this test
+
+def test_9x9_row():
+    '''
+    A few tests on rows of a 9x9 Sudoku board.
+    '''
+    b = sudoku.Board()
+    row = b.row(1)
+    expected_keys = ((x, 1) for x in range(b.size))
+    for ekey in expected_keys:
+    	assert ekey in row
+    # No negative numbers
+    assert (-1, 1) not in row
+    # Only squares with the right y-coordinate
+    assert (0, 0) not in row
+    # No keys above the size of the board
+    assert (b.size, 1) not in row
+
+
+def test_9x9_col():
+    '''
+    A few tests on rows of a 9x9 Sudoku board.
+    '''
+    b = sudoku.Board()
+    col = b.col(3)
+    expected_keys = ((3, y) for y in range(b.size))
+    for ekey in expected_keys:
+    	assert ekey in col
+    # No negative numbers
+    assert (3, -1) not in col
+    # Only squares with the right x-coordinate
+    assert (0, 0) not in col
+    # No keys above the size of the board
+    assert (3, b.size) not in col
+
+
+def test_9x9_box():
+    '''
+    A few tests on boxes of a 9x9 Sudoku board.
+    '''
+    b = sudoku.Board()
+    assert True
+
+
+def test_9x9_peers():
+    '''
+    Test peers.
+    '''
+    b = sudoku.Board()
+    peers = b.peers(3, 3)
+    expected_peers = set(  [(x, 3) for x in range(b.size)]
+                         + [(3, y) for y in range(b.size)]
+                         + [(3, 3), (3, 4), (3, 5), (4, 3), (4, 4), (4, 5), (5, 3), (5, 4), (5, 5)])
+    expected_peers.remove((3, 3))
+    for epeer in expected_peers:
+    	assert epeer in peers, '{} not in peers of (3, 3)'.format(epeer)
+
+
 def main():
     nose.main()
 

From 5a2df50e02b239e637c83c45eb1c4c2a59d62ddb Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@vmware.com>
Date: Thu, 29 Aug 2013 16:14:35 -0700
Subject: [PATCH 12/22] Add string test

---
 tests.py | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/tests.py b/tests.py
index d413bb1..32dabd1 100644
--- a/tests.py
+++ b/tests.py
@@ -101,6 +101,25 @@ def test_9x9_peers():
     	assert epeer in peers, '{} not in peers of (3, 3)'.format(epeer)
 
 
+def test_9x9_str():
+    '''
+    Test string generation/printing.
+    '''
+    b = sudoku.Board()
+    expected_str = '\n'.join(['. . . | . . . | . . .',
+                              '. . . | . . . | . . .',
+                              '. . . | . . . | . . .',
+                              '------+-------+------',
+                              '. . . | . . . | . . .',
+                              '. . . | . . . | . . .',
+                              '. . . | . . . | . . .',
+                              '------+-------+------',
+                              '. . . | . . . | . . .',
+                              '. . . | . . . | . . .',
+                              '. . . | . . . | . . .'])
+    assert str(b) == expected_str
+
+
 def main():
     nose.main()
 

From 9f4a775472ebb7143c4c263171588d60ba52e0fc Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@vmware.com>
Date: Thu, 29 Aug 2013 16:32:24 -0700
Subject: [PATCH 13/22] Add puzzles

Both via http://norvig.com/sudoku.html
- euler.txt: http://projecteuler.net/project/sudoku.txt
- norvig.txt: http://magictour.free.fr/top95
---
 puzzles/euler.txt  | 500 +++++++++++++++++++++++++++++++++++++++++++++
 puzzles/norvig.txt |  96 +++++++++
 2 files changed, 596 insertions(+)
 create mode 100644 puzzles/euler.txt
 create mode 100644 puzzles/norvig.txt

diff --git a/puzzles/euler.txt b/puzzles/euler.txt
new file mode 100644
index 0000000..be23f6a
--- /dev/null
+++ b/puzzles/euler.txt
@@ -0,0 +1,500 @@
+Grid 01
+003020600
+900305001
+001806400
+008102900
+700000008
+006708200
+002609500
+800203009
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+200080300
+060070084
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+000008006
\ No newline at end of file
diff --git a/puzzles/norvig.txt b/puzzles/norvig.txt
new file mode 100644
index 0000000..c8429cc
--- /dev/null
+++ b/puzzles/norvig.txt
@@ -0,0 +1,96 @@
+4.....8.5.3..........7......2.....6.....8.4......1.......6.3.7.5..2.....1.4......
+52...6.........7.13...........4..8..6......5...........418.........3..2...87.....
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+....14....3....2...7..........9...3.6.1.............8.2.....1.4....5.6.....7.8...
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+...5.1....9....8...6.......4.1..........7..9........3.8.....1.5...2..4.....36....
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+.26.39......6....19.....7.......4..9.5....2....85.....3..2..9..4....762.........4
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+1.....9...64..1.7..7..4.......3.....3.89..5....7....2.....6.7.9.....4.1....129.3.
+.........9......84.623...5....6...453...1...6...9...7....1.....4.5..2....3.8....9
+.2....5938..5..46.94..6...8..2.3.....6..8.73.7..2.........4.38..7....6..........5
+9.4..5...25.6..1..31......8.7...9...4..26......147....7.......2...3..8.6.4.....9.
+...52.....9...3..4......7...1.....4..8..453..6...1...87.2........8....32.4..8..1.
+53..2.9...24.3..5...9..........1.827...7.........981.............64....91.2.5.43.
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+...36....85.......9.4..8........68.........17..9..45...1.5...6.4....9..2.....3...
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+......8.16..2........7.5......6...2..1....3...8.......2......7..4..8....5...3....
+.2..........6....3.74.8.........3..2.8..4..1.6..5.........1.78.5....9..........4.
+.52..68.......7.2.......6....48..9..2..41......1.....8..61..38.....9...63..6..1.9
+....1.78.5....9..........4..2..........6....3.74.8.........3..2.8..4..1.6..5.....
+1.......3.6.3..7...7...5..121.7...9...7........8.1..2....8.64....9.2..6....4.....
+4...7.1....19.46.5.....1......7....2..2.3....847..6....14...8.6.2....3..6...9....
+......8.17..2........5.6......7...5..1....3...8.......5......2..3..8....6...4....
+963......1....8......2.5....4.8......1....7......3..257......3...9.2.4.7......9..
+15.3......7..4.2....4.72.....8.........9..1.8.1..8.79......38...........6....7423
+..........5724...98....947...9..3...5..9..12...3.1.9...6....25....56.....7......6
+....75....1..2.....4...3...5.....3.2...8...1.......6.....1..48.2........7........
+6.....7.3.4.8.................5.4.8.7..2.....1.3.......2.....5.....7.9......1....
+....6...4..6.3....1..4..5.77.....8.5...8.....6.8....9...2.9....4....32....97..1..
+.32.....58..3.....9.428...1...4...39...6...5.....1.....2...67.8.....4....95....6.
+...5.3.......6.7..5.8....1636..2.......4.1.......3...567....2.8..4.7.......2..5..
+.5.3.7.4.1.........3.......5.8.3.61....8..5.9.6..1........4...6...6927....2...9..
+..5..8..18......9.......78....4.....64....9......53..2.6.........138..5....9.714.
+..........72.6.1....51...82.8...13..4.........37.9..1.....238..5.4..9.........79.
+...658.....4......12............96.7...3..5....2.8...3..19..8..3.6.....4....473..
+.2.3.......6..8.9.83.5........2...8.7.9..5........6..4.......1...1...4.22..7..8.9
+.5..9....1.....6.....3.8.....8.4...9514.......3....2..........4.8...6..77..15..6.
+.....2.......7...17..3...9.8..7......2.89.6...13..6....9..5.824.....891..........
+3...8.......7....51..............36...2..4....7...........6.13..452...........8..
+
\ No newline at end of file

From 05976b51fbd1a53047d5eaa53790e268b55b051d Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 21:44:19 -0700
Subject: [PATCH 14/22] TODO and use self.possible_values instead of explicit
 range

---
 sudoku.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sudoku.py b/sudoku.py
index 9da9aa5..b5ca47a 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -120,7 +120,7 @@ class Board(dict):
         Clear the board. Resets each square's possible value list to the full range of possible values for this board.
         '''
         for square in self:
-            self[square] = list(range(1, self.size + 1))
+            self[square] = list(self.possible_values)
 
     def solve(self):
         for square, values in self.items():
@@ -143,6 +143,8 @@ class Board(dict):
                 self.eliminate(square, v)
             except ValueError:
                 raise
+        # TODO: To make this work right, I should probably also do the same as above for the values added *back* into
+        # the values for {square}.
         return True
 
     def eliminate(self, square, value):

From 3d69b671851c12a9b2b16f82f1a41dca51acb102 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 22:05:16 -0700
Subject: [PATCH 15/22] Fix printing -- had the x and y coordinates flipped

---
 sudoku.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index b5ca47a..e47228d 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -201,10 +201,10 @@ class Board(dict):
         lines = []
         box_lines = []
         square_size = len(str(self.size))
-        for x in range(self.size):
+        for y in range(self.size):
             row_squares = []
             box_squares = []
-            for y in range(self.size):
+            for x in range(self.size):
                 square = self.get(self._xy_key(x, y))
                 if len(square) == 1:
                     box_squares.append(str(square[0]).center(square_size))
@@ -218,7 +218,7 @@ class Board(dict):
             if len(box_lines) == self.box_size:
                 lines.append('\n'.join(box_lines))
                 box_lines = []
-                if x < self.size - 1:
+                if y < self.size - 1:
                     # Don't print a divider on the last line.
                     box_dividers = ['-' * ((square_size + 1) * self.box_size - 1) for box in range(self.box_size)]
                     lines.append('\n{}\n'.format('-+-'.join(box_dividers)))

From 6a5e13e345454af84b4ab92b870ab3c542914d4d Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 22:31:49 -0700
Subject: [PATCH 16/22] Add quick routines for parsing the puzzles in puzzles/

---
 puzzles.py | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 puzzles.py

diff --git a/puzzles.py b/puzzles.py
new file mode 100644
index 0000000..62f5199
--- /dev/null
+++ b/puzzles.py
@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+# Eryn Wells <eryn@erynwells.me>
+
+'''
+Parser for puzzles in the ./puzzles directory.
+'''
+
+import sudoku
+
+
+euler = []
+norvig = []
+
+
+def parse_euler(filename='./puzzles/euler.txt'):
+    with open(filename, 'r') as f:
+        puzzle_lines = f.readlines()
+
+    for puzzle in puzzle_lines:
+        # Chop the newline
+        if puzzle[-1] == '\n':
+            puzzle = puzzle[:-1]
+        print('Parsing puzzle: {}'.format(puzzle))
+        if len(puzzle) != 81:
+            continue
+        kwargs = {}
+        for idx in range(len(puzzle)):
+            sq = puzzle[idx]
+            if sq not in '1234567890.':
+                continue
+            sq_int = 0 if sq == '.' else int(sq)
+            x, y = int(idx % 9), int(idx / 9)
+            if sq_int != 0:
+                kwargs[sudoku.Board.xy_kwargs_key(x, y)] = sq_int
+        euler.append(sudoku.Board(**kwargs))
+
+
+def parse_norvig(filename='./puzzles/norvig.txt'):
+    with open(filename, 'r') as f:
+        puzzle_lines = f.readlines()
+
+    for puzzle in puzzle_lines:
+        # Chop the newline
+        if puzzle[-1] == '\n':
+            puzzle = puzzle[:-1]
+        print('Parsing puzzle: {}'.format(puzzle))
+        if len(puzzle) != 81:
+            continue
+        kwargs = {}
+        for idx in range(len(puzzle)):
+            sq = puzzle[idx]
+            if sq not in '1234567890.':
+                continue
+            sq_int = 0 if sq == '.' else int(sq)
+            x, y = int(idx % 9), int(idx / 9)
+            if sq_int != 0:
+                kwargs[sudoku.Board.xy_kwargs_key(x, y)] = sq_int
+        norvig.append(sudoku.Board(**kwargs))

From 09c6c4287f3be99a7bef1f94d6da50b6f865adf8 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 22:32:05 -0700
Subject: [PATCH 17/22] Convert Euler puzzles into Norvig format

---
 puzzles/euler.txt | 550 +++++-----------------------------------------
 1 file changed, 50 insertions(+), 500 deletions(-)

diff --git a/puzzles/euler.txt b/puzzles/euler.txt
index be23f6a..b0bb576 100644
--- a/puzzles/euler.txt
+++ b/puzzles/euler.txt
@@ -1,500 +1,50 @@
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From fdee9ed716f8bfbbfcf833fa41e7849be7ce6d83 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 22:32:15 -0700
Subject: [PATCH 18/22] Couple tweaks to help with parsing Euler and Norvig
 puzzles

- Make xy_key and xy_kwargs_key classmethods
---
 sudoku.py | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index e47228d..95dee07 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -29,7 +29,7 @@ class Board(dict):
             all possible values for the square. If an initial value was given, make sure it is one of the valid initial
             values. Raise a ValueError if not.
             '''
-            initial_value = kwargs.get('x{}y{}'.format(x, y))
+            initial_value = kwargs.get(Board.xy_kwargs_key(x, y))
             if initial_value is None:
                 return list(self.possible_values)
             if initial_value not in self.possible_values:
@@ -37,14 +37,23 @@ class Board(dict):
             return [initial_value]
 
         # Make the grid.
-        super(Board, self).__init__([(self._xy_key(x, y), kwget(x, y))
+        super(Board, self).__init__([(Board.xy_key(x, y), kwget(x, y))
                                      for x in range(self.size)
                                      for y in range(self.size)])
 
-    def _xy_key(self, x, y):
+    @classmethod
+    def xy_key(self, x, y):
         '''Given {x} and {y}, generate a key to refer to the square at coordinate (x, y) in the grid.'''
         return (int(x), int(y))
 
+    @classmethod
+    def xy_kwargs_key(self, x, y):
+        '''
+        Given {x} and {y}, generate a key to refer to the square in the __init__ kwargs at coordinate (x, y) in the
+        grid.
+        '''
+        return 'x{}y{}'.format(x, y)
+
     @property
     def solved(self):
         '''
@@ -205,7 +214,7 @@ class Board(dict):
             row_squares = []
             box_squares = []
             for x in range(self.size):
-                square = self.get(self._xy_key(x, y))
+                square = self.get(Board.xy_key(x, y))
                 if len(square) == 1:
                     box_squares.append(str(square[0]).center(square_size))
                 else:
@@ -223,5 +232,3 @@ class Board(dict):
                     box_dividers = ['-' * ((square_size + 1) * self.box_size - 1) for box in range(self.box_size)]
                     lines.append('\n{}\n'.format('-+-'.join(box_dividers)))
         return ''.join(lines)
-
-

From 81e3296f6ff4302f3e2ea1c6aade7c5812d1630e Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Thu, 29 Aug 2013 22:46:38 -0700
Subject: [PATCH 19/22] Create keys then assign values in __init__

---
 sudoku.py | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index 95dee07..ea78cc2 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -23,23 +23,18 @@ class Board(dict):
         # The range of possible values for a square.
         self.possible_values = range(1, self.size + 1)
 
-        def kwget(x, y):
-            '''
-            Try to get an initial value for square ({x}, {y}) from the given kwargs. If none exists, return a list of
-            all possible values for the square. If an initial value was given, make sure it is one of the valid initial
-            values. Raise a ValueError if not.
-            '''
-            initial_value = kwargs.get(Board.xy_kwargs_key(x, y))
-            if initial_value is None:
-                return list(self.possible_values)
-            if initial_value not in self.possible_values:
-                raise ValueError('Invalid initial value for square ({}, {}): {}'.format(x, y, initial_value))
-            return [initial_value]
-
         # Make the grid.
-        super(Board, self).__init__([(Board.xy_key(x, y), kwget(x, y))
+        super(Board, self).__init__([(Board.xy_key(x, y), list(self.possible_values))
                                      for x in range(self.size)
                                      for y in range(self.size)])
+        for square in self:
+            initial_value = kwargs.get(Board.xy_kwargs_key(*square))
+            if initial_value is None:
+                continue
+            if initial_value not in self.possible_values:
+                raise ValueError('Invalid initial value for square ({}, {}): {}'.format(x, y, initial_value))
+            LOG.debug('Setting initial value of {} to {}'.format(square, initial_value))
+            self[square] = [initial_value]
 
     @classmethod
     def xy_key(self, x, y):
@@ -121,7 +116,7 @@ class Board(dict):
         # Generate a dictionary of all the squares in the row, column, and box containing the given square.
         peers = dict(list(self.row(y).items()) + list(self.col(x).items()) + list(self.box(x, y).items()))
         # Remove the given square.
-        del peers[self._xy_key(x, y)]
+        del peers[Board.xy_key(x, y)]
         return peers
 
     def clear(self):

From cc5e35ff8194ee29390b86a14255b95a11348f5b Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Fri, 30 Aug 2013 10:11:44 -0700
Subject: [PATCH 20/22] Working on search()

---
 sudoku.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sudoku.py b/sudoku.py
index ea78cc2..ea1bbd8 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -135,6 +135,14 @@ class Board(dict):
                     raise
         return self.solved
 
+    def search(self):
+        if self.solved:
+            return True
+
+        # Chose the square with the fewest possible values.
+        _, smallest = min((len(self[sq]), sq) for sq in self if len(self[sq]) > 1)
+        # Deepcopy the board.
+
     def assign(self, square, value):
         '''
         Assign {value} to {square}. {value} is expected to be an iterable (a list). {key} should be a valid (x, y)

From 6cc3fed4b3e4c6d60ed3153d42ae1ceb6612f931 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Fri, 30 Aug 2013 17:09:41 -0700
Subject: [PATCH 21/22] Implement search

- Remove __setitem__; it was getting in the way...
- deepcopy the board for each trial in search()
---
 sudoku.py | 40 +++++++++++++++++++++-------------------
 1 file changed, 21 insertions(+), 19 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index ea1bbd8..efdabc3 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -5,6 +5,7 @@
 A Sudoku solver.
 '''
 
+import copy
 import logging
 import math
 
@@ -34,7 +35,7 @@ class Board(dict):
             if initial_value not in self.possible_values:
                 raise ValueError('Invalid initial value for square ({}, {}): {}'.format(x, y, initial_value))
             LOG.debug('Setting initial value of {} to {}'.format(square, initial_value))
-            self[square] = [initial_value]
+            self.assign(square, [initial_value])
 
     @classmethod
     def xy_key(self, x, y):
@@ -119,29 +120,36 @@ class Board(dict):
         del peers[Board.xy_key(x, y)]
         return peers
 
-    def clear(self):
+    def clear(self, squares=None):
         '''
         Clear the board. Resets each square's possible value list to the full range of possible values for this board.
         '''
-        for square in self:
-            self[square] = list(self.possible_values)
+        for square in (self if squares is None else squares):
+            self.assign(square, list(self.possible_values))
 
     def solve(self):
-        for square, values in self.items():
-            if len(values) == 1:
-                try:
-                    self.assign(square, values)
-                except ValueError:
-                    raise
-        return self.solved
+        return self.search()
 
     def search(self):
+        '''
+        Search for a solution, depth-first. Return the solved Board as a new instance of this class.
+        '''
         if self.solved:
-            return True
+            return self
 
         # Chose the square with the fewest possible values.
         _, smallest = min((len(self[sq]), sq) for sq in self if len(self[sq]) > 1)
         # Deepcopy the board.
+        for v in self[smallest]:
+            trial_board = copy.deepcopy(self)
+            try:
+                trial_board.assign(smallest, [v])
+                if trial_board.search():
+                    return trial_board
+            except ValueError:
+                continue
+        raise ValueError('No possible solution found.')
+
 
     def assign(self, square, value):
         '''
@@ -196,19 +204,13 @@ class Board(dict):
                 raise ValueError('No place for value {} to go in unit {}; board is now invalid'.format(value, unit))
             elif len(places) == 1:
                 LOG.debug('One place for value {} to be in unit {}; setting'.format(value, unit))
-                self[places[0]] = [value]
+                self.assign(places[0], [value])
         return True
 
     def __delitem__(self, key):
         # Don't allow deleting keys from self.
         pass
 
-    def __setitem__(self, key, value):
-        if key not in self:
-            # Don't allow adding new keys, only changes to existing ones.
-            raise KeyError('Key {} is not a valid coordinate pair.'.format(key))
-        self.assign(key, value)
-
     def __str__(self):
         lines = []
         box_lines = []

From e004d319e31c6f9b642bac5ded4047869e9b19bb Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Fri, 6 Oct 2017 20:27:01 -0700
Subject: [PATCH 22/22] IDK what this WIP is

---
 sudoku.py | 38 ++++++++++++++++++--------------------
 1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/sudoku.py b/sudoku.py
index efdabc3..964e6be 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -140,15 +140,18 @@ class Board(dict):
         # Chose the square with the fewest possible values.
         _, smallest = min((len(self[sq]), sq) for sq in self if len(self[sq]) > 1)
         # Deepcopy the board.
+        trials = []
         for v in self[smallest]:
             trial_board = copy.deepcopy(self)
-            try:
-                trial_board.assign(smallest, [v])
-                if trial_board.search():
-                    return trial_board
-            except ValueError:
-                continue
-        raise ValueError('No possible solution found.')
+            if trial_board.assign(smallest, [v]):
+                trials.append(trial_board)
+                trial_board.search()
+            else:
+                trials.append(None)
+        for t in trials:
+            if t is not None:
+                return t
+        return False
 
 
     def assign(self, square, value):
@@ -159,12 +162,8 @@ class Board(dict):
         LOG.debug('Assigning values {} to square {}.'.format(value, square))
         removed_values = set(self[square]) - set(value)
         for v in removed_values:
-            try:
-                self.eliminate(square, v)
-            except ValueError:
-                raise
-        # TODO: To make this work right, I should probably also do the same as above for the values added *back* into
-        # the values for {square}.
+            if not self.eliminate(square, v):
+                return False
         return True
 
     def eliminate(self, square, value):
@@ -186,25 +185,24 @@ class Board(dict):
         if len(self[square]) == 0:
             # Whoops. Removed the last value... We have a contradiction now.
             LOG.error('Removed last value from square {}'.format(square))
-            raise ValueError('Removed last value from square {}; board is now invalid'.format(square))
+            return False
         elif len(self[square]) == 1:
             # One value left in this square. Propagate changes to its peers.
             LOG.debug('One value left in square {}; eliminating {} from its peers'.format(square, self[square][0]))
-            try:
-                for peer in self.peers(*square):
-                    self.eliminate(peer, self[square][0])
-            except ValueError:
-                raise
+            for peer in self.peers(*square):
+                if not self.eliminate(peer, self[square][0]):
+                    return False
 
         # (2) If a unit has only one square for a value, put it there.
         for unit in (self.row(square[1]), self.col(square[0]), self.box(*square)):
             places = [sq for sq in unit if value in unit[sq]]
             if len(places) == 0:
                 LOG.error('No place for value {} to go in unit {}'.format(value, unit))
-                raise ValueError('No place for value {} to go in unit {}; board is now invalid'.format(value, unit))
+                return False
             elif len(places) == 1:
                 LOG.debug('One place for value {} to be in unit {}; setting'.format(value, unit))
                 self.assign(places[0], [value])
+
         return True
 
     def __delitem__(self, key):