Skyscraper sudoku

In a grid of 6 by 6 squares you need to place a skyscraper in each square with only some clues:

• The height of the skyscrapers is between 1 and 6
• No two skyscrapers in a row or column may have the same number of floors
• A clue is the number of skyscrapers that you can see in a row or column from the outside
• Higher skyscrapers block the view of lower skyscrapers located behind them

To understand how the puzzle works, this is an example of a row with 2 clues. Seen from the left there are 6 buildings visible while seen from the right side only 1:

6							1

There is only one way in which the skyscrapers can be placed. From left-to-right all six buildings must be visible and no building may hide behind another building:

6	1	2	3	4	5	6	1

Task:

Input: The clues in an array of 24 items ordered around the clock. Index:

	0	1	2	3	4	5
23							6
22							7
21							8
20							9
19							10
18							11
	17	16	15	14	13	12

• If no clue is available, add value 0
• Each puzzle has only one possible solution

Output: Array of skyscrapers heights linewise (top to bottom, left to right).

Example of a 6 by 6 puzzle with the solution:

				2	2
	5	6	1	4	3	2
	4	1	3	2	6	5
3	2	3	6	1	5	4
	6	5	4	3	2	1	6
4	1	2	5	6	4	3	3
4	3	4	2	5	1	6
					4

Input: '0,0,0,2,2,0,0,0,0,6,3,0,0,4,0,0,0,0,4,4,0,3,0,0'

Output: '5,6,1,4,3,2,4,1,3,2,6,5,2,3,6,1,5,4,6,5,4,3,2,1,1,2,5,6,4,3,3,4,2,5,1,6'