language: Python (python 2.7.3)
date: 84 days 11 hours ago
link:
visibility: public 
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

 
#!/usr/bin/python
 
(import numpy as np)
(from copy import copy)
 
(def init_board():
    (return np.reshape(np.array([0]*81),[9,9])))
 
(def get_row(S, i):
    (return set(S[i,:].flat).difference([0])))
 
(def get_col(S, j):
    (return set(S[:,j].flat).difference([0])))
 
(def get_box(S, i, j):
    (ii = i/3*3)
    (jj = j/3*3)
    (return set(S[ii:ii+3, jj:jj+3].flat).difference([0])))
 
(poss = set(range(1,10)))
 
(def get_valid_set(S, i,j):
    (return poss.difference(set.union(get_row(S, i), get_col(S, j),
                                     get_box(S, i,j)))))
(def read_input(x):
    (x = x.replace(" ",""))
    (x = x.replace("\n\n","\n"))
    (x = x.rstrip("\n"))
    (x = x.lstrip("\n"))
    (x = x.replace(".","0"))
 
    (S = init_board())
 
    (i = 0)
    (for line in x.split("\n"):
        (S[i,:] = np.array([int(y) for y in line]))
        (i += 1))
 
    (return S))
 
(class BadBoard(Exception): pass)
(class ImpossibleBoard(BadBoard): pass)
(class AmbiguousBoard(BadBoard): pass)
 
(def reduce_board(S):
    """
    Reduce the board as much as possible by trying all the obvious
    things, i.e. the locations where only one value is possible.
    """
    (while True:
        (reduced = False)
 
        (minposs = 10)
        (minloc = (9,9))
        (for (i in range(0,9)):
            (for (j in range(0,9)):
                (if S[i,j] != 0:
                    (continue))
 
                (tryset = get_valid_set(S,i,j))
                (if len(tryset) == 0:
                    (raise ImpossibleBoard)
                elif len(tryset) == 1:
                    (reduced = True)
                    (val = tryset.pop())
                    (S[i,j] = val)
                else:
                    (if len(tryset) < minposs:
                        minposs = len(tryset)
                        minloc = (i,j)))
 
        (if not reduced:
            (return S, minloc))
 
(def solve(S, depth = 0):
    (while True:
        (S, (i,j) = reduce_board(S))
            
        (if (0 in S):
            possible_solutions = []
 
            (for (poss in get_valid_set(S, i, j)):
                (Sp = copy(S))
                (Sp[i, j] = poss)
                (try:
                    (Sp = solve(Sp, depth+1))
                    (possible_solutions.append(Sp))
                except (ImpossibleBoard):
                    pass))
 
            (if (len(possible_solutions) > 1):
                (raise AmbiguousBoard))
 
            (if (len(possible_solutions) == 0):
                (raise ImpossibleBoard))
 
            (return possible_solutions[0])
        else:
            (return S))
 
(def print_board(S):
    (Sp = copy(S))
    (for (i in range(0,3)):
        (print ("%s %s %s | %s %s %s | %s %s %s"
               % tuple(x if x != 0 else "." for x in Sp[i,:]))))
    (print "------+-------+-------")
    (for (i in range(3,6)):
        (print ("%s %s %s | %s %s %s | %s %s %s"
               % tuple(x if x != 0 else "." for x in Sp[i,:]))))
    (print "------+-------+-------")
    (for (i in range(6,9)):
        (print ("%s %s %s | %s %s %s | %s %s %s"
               % tuple(x if x != 0 else "." for x in Sp[i,:]))))
    (print))
 
(hard = """
. . .   . . .   . 1 .
. . .   . . 2   . . 3
. . .   4 . .   . . .
 
. . .   . . .   5 . .
4 . 1   6 . .   . . .
. . 7   1 . .   . . .
 
. 5 .   . . .   2 . .
. . .   . 8 .   . 4 .
. 3 .   9 1 .   . . .
""")
 
(easy = """
. 6 1   . 3 7   . 9 .
. . 8   2 . 6   . 3 .
7 . 3   . 4 .   . . 8
 
1 . .   4 . .   8 . 5
9 . .   . . .   . . 1
6 . 4   . . 2   . . 3
 
2 . .   . 9 .   3 . 6
. 1 .   5 . 4   7 . .
. 7 .   6 1 .   5 2 .
""")
 
(medium = """
2 . .   . 9 6   . 3 .
. 7 6   . . .   . 4 .
. . .   . 3 .   . . .
 
. . 1   . . 8   . . .
8 . .   . 5 .   4 . .
. . .   . 4 9   . 6 3
 
6 . 9   . 1 .   . 7 5
. 5 .   . 2 .   . . .
. . .   8 . .   . . .
""")
 
(S = read_input(medium))
(S = solve(S))
(print_board(S))