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local function permutation(a, n, cb)
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if n == 0 then
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cb(a)
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else
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for i = 1, n do
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a[i], a[n] = a[n], a[i]
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permutation(a, n - 1, cb)
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a[i], a[n] = a[n], a[i]
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end
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end
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end
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--Usage
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local function callback(a)
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print('{'..table.concat(a, ', ')..'}')
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end
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permutation({1,2,3}, 3, callback)
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