Light Up Light Up
Simple
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This mission is an adaptation of the "Light Up" game (from Simon Tatham's Portable Puzzle Collection). If you are lost or just want to play, the game is available here.

You're on a rectangular grid and you have to light up all the cells. For that, you need to put some lights in dark cells (so no light should illuminate another). The lights that you have illuminate in the four directions from wall to wall. And there are constraints: some walls must have a given number of lights close to them.

The grid will be represented by a tuple of strings. Cells that are in the dark will be represented by ' ', walls by 'X' and numbers '0', '1', '2', '3' and '4'.

You have to return the coordinates of all the lights you want to place to illuminate the entire grid.

7x7 example image

Possible lights: [(0, 5), (5, 6), (3, 3), (4, 4), (0, 0), (2, 2),
                  (6, 5), (6, 1), (5, 0), (1, 1), (1, 6)]

('    1  ',
 '   0X  ',
 'X2     ',
 ' 0   0 ',
 '     11',
 '  X0   ',
 '  1    ')

Input: A tuple of strings.

Output: An iterable of tuples/lists of two integers.

Example:

list(checkio(('    1  ',
              '   0X  ',
              'X2     ',
              ' 0   0 ',
              '     11',
              '  X0   ',
              '  1    '))) = [(0, 5), (5, 6), (3, 3), (4, 4), (0, 0), (2, 2),
                              (6, 5), (6, 1), (5, 0), (1, 1), (1, 6)]

To play the puzzles / tests yourself: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Preconditions:

  • Given puzzles are solvable and there is only one solution (when the coordinates are sorted).
  • 7 ≤ len(grid) ≤ 50 and 7 ≤ len(grid[0]) ≤ 60.
  • all(len(row) == len(grid[0]) for row in grid).