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problem_096.py
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problem_096.py
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from functools import cache
@cache
def relevant(pos):
x, y = pos
return (
{(x, j) for j in range(9)}
| {(i, y) for i in range(9)}
| {(x // 3 * 3 + i, y // 3 * 3 + j) for j in range(3) for i in range(3)}
)
class Sudoku:
def __init__(self, vals):
self.grid = {}
self.legal = {
(x, y): set(range(1, 10)) for y in range(9) for x in range(9)
}
for y in range(9):
for x in range(9):
if (val := next(vals)) != 0:
self.set((x, y), val)
def __str__(self):
return (
"\n".join(
" ".join(
str(self.grid[(x, y)]) if (x, y) in self.grid else "\u00b7"
for x in range(9)
)
for y in range(9)
)
+ "\n"
)
def set(self, pos, val):
self.grid[pos] = val
for r in relevant(pos):
self.legal[r].discard(val)
def unset(self, pos):
del self.grid[pos]
for r in relevant(pos):
self.legal[r] = set(range(1, 10)) - {
self.grid[q] for q in relevant(r) if q in self.grid
}
def solutions(self):
empty = {
(x, y)
for y in range(9)
for x in range(9)
if (x, y) not in self.grid
}
if len(empty) > 0:
pos = min(empty, key=lambda pos: len(self.legal[pos]))
for guess in self.legal[pos].copy():
self.set(pos, guess)
yield from self.solutions()
self.unset(pos)
else:
yield self
def solve(self):
return next(self.solutions())
def parse(file):
lines = open(file).readlines()
return [
Sudoku(int(d) for line in lines[i : i + 9] for d in line.strip())
for i in range(1, len(lines), 10)
]
def main():
return sum(
100 * solved.grid[(0, 0)]
+ 10 * solved.grid[(1, 0)]
+ solved.grid[(2, 0)]
for solved in (s.solve() for s in parse("data/096"))
)
# 24702