Update Shuffle #869
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Update Shuffle #869
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according to https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle `checks if j ≠ i may be omitted`, and also remove checking logic will optimise performance(tested by 100000 times random).
richard-ash
reviewed
Mar 24, 2019
| @@ -96,9 +96,6 @@ public func shuffledArray(_ n: Int) -> [Int] { | |||
| var a = [Int](repeating: 0, count: n) | |||
| for i in 0..<n { | |||
| let j = Int.random(in: 0...i) | |||
| if i != j { | |||
| a[i] = a[j] | |||
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Removing this line breaks the algorithm. You're right the check if i != j is unnecessary however you still need the line a[i] = a[j]
| @@ -30,9 +30,6 @@ public func shuffledArray(_ n: Int) -> [Int] { | |||
| var a = Array(repeating: 0, count: n) | |||
| for i in 0..<n { | |||
| let j = random(i + 1) | |||
| if i != j { | |||
| a[i] = a[j] | |||
|
Cool, thanks for the update 🙂 |
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according to https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
checks if j ≠ i may be omitted, and also remove checking logic will optimise performance(tested by 100000 times random).Checklist
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