13 4 Queens Results 0 [-1, -1, -1, -1] 1 [0, -1, -1, -1] 2 [0, 2, -1, -1] Backtrack 2 [0, 3, -1, -1] 3 [0, 3, 1, -1] Backtrack 1 [1, -1, -1, -1] 2 [1, 3, -1, -1] 3 [1, 3, 0, -1] 4 [1, 3, 0, 2] Success!.
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