On Wednesday, March 25, 2015 at 4:39:40 AM UTC-7, Marko Rauhamaa wrote:
> A lot of discussion was generated by the good, old fibonacci sequence. I
> have yet to find practical use for fibonacci numbers. However, the
> technique behind a sudoku solver come up every now and again in
> practical situations.
>
> I post below a sudoku solver. I eagerly await neater implementations (as
> well as bug reports).
>
> Usage:
> ========================================================================
> ./sudoku.py <sudoku.dat
> ========================================================================
>
> sudoku.dat:
> ========================================================================
> 7 . . . . . 6 . .
> . 2 . 8 . 6 . 7 .
> . . . 4 3 . . 9 .
> 5 1 . . . . 4 . 3
> . . 9 . . . . 1 .
> . . . . 4 2 . . 5
> . . . 9 . . . . 8
> . . 6 . . . . 5 .
> . . . . . . . 6 .
> ========================================================================
>
> output:
> ========================================================================
> 7 8 4 2 9 5 6 3 1
> 9 2 3 8 1 6 5 7 4
> 6 5 1 4 3 7 8 9 2
> 5 1 8 6 7 9 4 2 3
> 2 4 9 3 5 8 7 1 6
> 3 6 7 1 4 2 9 8 5
> 1 7 5 9 6 3 2 4 8
> 8 3 6 7 2 4 1 5 9
> 4 9 2 5 8 1 3 6 7
>
> ========================================================================
>
> sudoku.py:
> ========================================================================
> #!/usr/bin/env python3
>
> import sys
>
> M = 3
> N = M * M
> Q = N * N
>
> candidates = list(range(1, N + 1))
>
> def main():
> board = []
> for n in sys.stdin.read().split():
> try:
> board.append(int(n))
> except ValueError:
> board.append(None)
> solve(board)
>
> def solve(board, slot=0):
> if slot == Q:
> report(board)
> elif board[slot] is None:
> for candidate in candidates:
> if good(board, slot, candidate):
> board[slot] = candidate
> solve(board, slot + 1)
> board[slot] = None
> else:
> solve(board, slot + 1)
>
> def good(board, slot, candidate):
> (shelf, row), (stack, col) = (divmod(x, M) for x in divmod(slot, N))
> for i in range(M):
> for j in range(M):
> if candidate in (board[(i * M + j) * N + stack * M + col],
> board[(shelf * M + row) * N + i * M + j],
> board[(shelf * M + i) * N + stack * M + j]):
> return False
> return True
>
> def report(board):
> print("\n".join(
> " ".join(str(board[row * N + col])
> for col in range(N))
> for row in range(N)))
> print()
>
> if __name__ == '__main__':
> main()
> ========================================================================
>
>
> Marko
You say "neater implementation"
I'll send you to the code-golf site:
http://codegolf.stackexchange.com/a/446/38632 this is brute force. There are
some really good implementations in other languages that arent brute force.
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