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

You have to divide a rectangular grid into rectangles, so that each rectangle contains exactly one cell with a non-empty number and the rectangle area is equal to this number.

The grid will be represented by a list of list of integers.
A rectangle will be represented by a tuple or list of four integers:

• the first two are the coordinates of the top left corner ;
• the last two are the coordinates of the bottom right corner.

[[3, 0, 0, 0, 0, 2],          {(0, 0, 0, 2), (1, 2, 3, 2),
 [2, 0, 0, 4, 0, 0],           (1, 1, 5, 1), (1, 0, 2, 0),
 [0, 5, 0, 0, 0, 0],   ===\    (3, 0, 5, 0), (2, 4, 4, 5),
 [3, 0, 3, 2, 0, 0],   ===/    (0, 5, 1, 5), (0, 3, 1, 4),
 [0, 0, 2, 0, 0, 6],           (2, 3, 3, 3), (4, 2, 4, 3),
 [0, 0, 0, 4, 0, 0]]           (5, 2, 5, 5)}              

Rectangle A starts at (0, 0) and ends at (0, 2).
Rectangle B starts at (1, 2) and ends at (3, 2).
Rectangle C starts at (1, 1) and ends at (5, 1).
...
Rectangle K starts at (5, 2) and ends at (5, 5).

Input: A list of list of integers.

Output: An iterable/list/set of tuple/list of four integers.

rectangles([[3, 0, 0, 0, 0, 2],
            [2, 0, 0, 4, 0, 0],
            [0, 5, 0, 0, 0, 0],
            [3, 0, 3, 2, 0, 0],
            [0, 0, 2, 0, 0, 6],
            [0, 0, 0, 4, 0, 0]]) == {(0, 0, 0, 2), (1, 2, 3, 2), (1, 1, 5, 1), (1, 0, 2, 0),
                                     (3, 0, 5, 0), (2, 4, 4, 5), (0, 5, 1, 5), (0, 3, 1, 4),
                                     (2, 3, 3, 3), (4, 2, 4, 3), (5, 2, 5, 5)}

Preconditions:

• All puzzles have one and only one solution.
• 6 ≤ len(grid) ≤ 50 and 6 ≤ len(grid[0]) ≤ 50.
• all(len(row) == len(grid[0]) for row in grid).