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is_valid_sudoku.py
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is_valid_sudoku.py
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import collections
import math
from test_framework import generic_test
# Check if a partially filled matrix has any conflicts.
def is_valid_sudoku(partial_assignment):
# Return True if subarray
# partial_assignment[start_row:end_row][start_col:end_col] contains any
# duplicates in {1, 2, ..., len(partial_assignment)}; otherwise return
# False.
def has_duplicate(block):
block = list(filter(lambda x: x != 0, block))
return len(block) != len(set(block))
n = len(partial_assignment)
# Check row and column constraints.
if any(
has_duplicate([partial_assignment[i][j] for j in range(n)])
or has_duplicate([partial_assignment[j][i] for j in range(n)])
for i in range(n)):
return False
# Check region constraints.
region_size = int(math.sqrt(n))
return all(not has_duplicate([
partial_assignment[a][b]
for a in range(region_size * I, region_size * (
I + 1)) for b in range(region_size * J, region_size * (J + 1))
]) for I in range(region_size) for J in range(region_size))
# Pythonic solution that exploits the power of list comprehension.
def is_valid_sudoku_pythonic(partial_assignment):
region_size = int(math.sqrt(len(partial_assignment)))
return max(
collections.Counter(k for i, row in enumerate(partial_assignment)
for j, c in enumerate(row) if c != 0
for k in ((i, str(c)), (str(c), j),
(i / region_size, j / region_size,
str(c)))).values(),
default=0) <= 1
if __name__ == '__main__':
exit(
generic_test.generic_test_main("is_valid_sudoku.py",
"is_valid_sudoku.tsv", is_valid_sudoku))