Welcome, guest | Sign In | My Account | Store | Cart
1

This is a simple text based Sadoku puzzle solver.

See http://www.websudoku.com/ for more details.

Python, 224 lines
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
'''
Simple text based Sudoku solver.
'''
__author__ = 'Justin Shaw'

import copy

def uniqueInsert(l, v):
    '''
    Add v to list if it is not already there, else raise ValueError
    '''
    if v is not None:
        if v in l:
            raise ValueError('list already contains value %s' % v)
        assert 0 < v < 10, 'Only 1-9 allowed, got %s' % v
        l.append(v)
        
class Sudoku:
    def submat(self, i, j):
        '''
        Return i, j 3x3 submatrix of self.
        '''
        mat = self.mat
        out = []
        for srow_i in range(3):
            row = []
            for scol_i in range(3):
                v = mat[i * 3 + srow_i][j * 3 + scol_i]
                row.append(v)
            out.append(row)
        return out
    
    def copy(self):
        return Sudoku(copy.deepcopy(self.mat))
    
    def add(self, v, i, j):
        '''
        Fill in an entry in self.mat
        '''
        self.mat[i][j] = v
        uniqueInsert(self.rows[i], v)
        uniqueInsert(self.cols[j], v)
        sub_i = i // 3 * 3 + j // 3
        uniqueInsert(self.subs[sub_i], v)

    def __init__(self, mat):
        '''
        Create a new Sudoku instance.
        mat -- 9x9 array of digits 1-9
               or None if no value is known for that spot
        '''
        self.mat = mat

        # keep track of all values used in each row, column and sub-matrix.
        rows = [[] for i in range(9)]
        cols = [[] for i in range(9)]
        subs = [[] for i in range(9)]
        
        for row_i in range(9):
            for col_i in range(9):
                v = self.mat[row_i][col_i]
                uniqueInsert(rows[row_i], v)
                uniqueInsert(cols[col_i], v)
        for srow_i in range(3):
            for scol_i in range(3):
                sub = self.submat(srow_i, scol_i)
                for i in range(3):
                    for j in range(3):
                        v = sub[i][j]
                        sub_i = srow_i * 3 + scol_i
                        uniqueInsert(subs[sub_i], v)
        self.rows = rows
        self.cols = cols
        self.subs = subs
        
    def __repr__(self):
        out = ''
        for i in range(9):
            if i % 3 == 0:
                out += '+-------+-------+-------+\n'
            for j in range(9):
                if j % 3 == 0:
                    out += '| '
                v = self.mat[i][j]
                if v is not None:
                    out += '%1d ' % v
                else:
                    out +=  '  '
            out += '|\n'
        out += '+-------+-------+-------+\n'
        return out

    def solve(self):
        '''
        Solve for the unknown positions of the puzzle
        '''
        
        min_poss = 9 # Minimum possible number of choices for a cell
        done = True
        for i in range(9):
            for j in range(9):
                sub_i = i // 3 * 3 + j // 3 # sub-matrix index
                v = self.mat[i][j]
                if v:
                    pass
                else:
                    # not all values filled out so we are not done yet
                    done = False
                    all = set(range(1, 10))

                    # determine all possible values for this cell
                    possible = (all.difference(self.rows[i])
                                .difference(self.cols[j])
                                .difference(self.subs[sub_i]))

                    # see if we have run into a brick wall
                    if len(possible) == 0:
                        raise ValueError('Sudoku not solvable')
                    elif len(possible) < min_poss:
                        
                        # keep track of cell with smallest number of choices
                        min_poss = len(possible)
                        best = possible
                        min_i = i
                        min_j = j
        if done:
            out = self
        else:
            
            # Try these possibilities and recurse
            for b in best:
                print min_i, min_j, b
                trial = self.copy()
                trial.add(b, min_i, min_j)
                print trial
                try:
                    soln = trial.solve()
                    break
                except ValueError:
                    soln = None
            if soln is None:
                print self
                raise ValueError('Sudoku not solvable')
            out = soln
        return out
                
N = None
easy = [
    [7, N, N,   1, 5, N,   N, N, 8],
    [N, N, 4,   N, N, 2,   N, N, N],
    [N, N, N,   N, N, 4,   5, 6, N],

    [6, N, N,   N, N, N,   N, 2, 9],
    [5, N, 2,   N, N, N,   8, N, 4],
    [3, 4, N,   N, N, N,   N, N, 1],

    [N, 3, 8,   6, N, N,   N, N, N],
    [N, N, N,   2, N, N,   9, N, N],
    [1, N, N,   N, 8, N,   N, N, 3]
    ]

hard = [
    [N, 4, N,   N, N, 7,   9, N, N],
    [N, N, 8,   5, 3, 9,   N, N, N],
    [N, 6, N,   N, N, N,   2, N, 3],

    [N, N, N,   N, N, 2,   5, N, N],
    [N, 8, 6,   N, N, N,   1, 4, N],
    [N, N, 9,   8, N, N,   N, N, N],

    [6, N, 3,   N, N, N,   N, 9, N],
    [N, N, N,   9, 8, 6,   3, N, N],
    [N, N, 1,   4, N, N,   N, 6, N]
    ]


evil = [
    [4, 2, N,   N, N, N,   N, 1, N],
    [N, N, N,   5, 4, N,   N, 3, N],
    [N, N, 6,   N, N, 7,   N, N, N],

    [N, N, N,   N, N, N,   2, 7, 9],
    [N, 1, N,   N, N, N,   N, 6, N],
    [3, 4, 2,   N, N, N,   N, N, N],

    [N, N, N,   9, N, N,   3, N, N],
    [N, 6, N,   N, 3, 8,   N, N, N],
    [N, 8, N,   N, N, N,   N, 5, 7]
    ]

blank = [
    [N, N, N,   N, N, N,   N, N, N],
    [N, N, N,   N, N, N,   N, N, N],
    [N, N, N,   N, N, N,   N, N, N],

    [N, N, N,   N, N, N,   N, N, N],
    [N, N, N,   N, N, N,   N, N, N],
    [N, N, N,   N, N, N,   N, N, N],

    [N, N, N,   N, N, N,   N, N, N],
    [N, N, N,   N, N, N,   N, N, N],
    [N, N, N,   N, N, N,   N, N, N]
    ]

import time
easy = Sudoku(easy)
hard = Sudoku(hard)
evil = Sudoku(evil)
print
print 'easy'
print easy
time.sleep(2)
easy.solve()
print
print 'hard'
print hard
time.sleep(2)
hard.solve()
print
print 'evil'
print evil
print
time.sleep(2)
evil.solve()

Hey, if you can't sleep because of Sudoku, may as well solve the general problem!

1 comment

Justin Shaw (author) 9 years, 3 months ago  # | flag

OOps. def digits(): return set(range(1, 10))

Add a comment

Sign in to comment