Add SICP JS solutions #2
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| require(num_queens <= board_size); | ||
| const possible_positions = enum_list(1, board_size); | ||
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| const result = accumulate( |
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Is there a reason to use accumulate, other than the fact that we want to perform the process num_queens times?
If not, can \ should we use for_each ?
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Yes, accumulate gives us the positions that we have already, with the variable so_far. It is used in checking whether potential new rows and columns can be added.
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This PR adds two solutions for the n-queens puzzle using the Source 3 non-deterministic language. Each of them makes use of the generate-and-test paradigm.
The first (
queens_slow) uses non-determinism for generating both the row and column for each position. It does so in an optimized manner, testing the corresponding condition as soon as the choice is generated, thereby reducing the search space. However, this is not enough to yield a quick solution when N = 8. This solution also gives repeated solutions (i.e different permutations that have all the same positions) upon backtracking.The second (
queens_fast) uses non-determinism in picking only the row and not the column of each position, with the columns being fixed. This further reduces the search space, yielding a quick solution when N = 8.Example:
