16 lines
411 B
Swift
16 lines
411 B
Swift
func perms<T>(var ar: [T]) -> [[T]] {
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return heaps(&ar, ar.count)
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}
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func heaps<T>(inout ar: [T], n: Int) -> [[T]] {
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return n == 1 ? [ar] :
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Swift.reduce(0..<n, [[T]]()) {
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(var shuffles, i) in
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shuffles.extend(heaps(&ar, n - 1))
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swap(&ar[n % 2 == 0 ? i : 0], &ar[n - 1])
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return shuffles
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}
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}
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perms([1, 2, 3]) // [[1, 2, 3], [2, 1, 3], [3, 1, 2], [1, 3, 2], [2, 3, 1], [3, 2, 1]]
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