sleepsort.swift

import Foundation
import Dispatch

public struct SleepSort {
    /// Dispatches a block after `secs` seconds
    static func dispatch(after secs: Double, block: @escaping () -> Void) {
        #if os(Linux)
            let delay = Double(CLOCKS_PER_SEC) * secs
        #else
            let delay = Double(NSEC_PER_SEC) * secs
        #endif
        let dT = DispatchTime(uptimeNanoseconds:DispatchTime.now().rawValue + UInt64(delay))
        if #available(OSX 10.10, *) {
            DispatchQueue
                .global(qos: .default)
                .asyncAfter(deadline:  dT, execute: block)
        }
    }
    
    // Return sleep-sorted integer array
    public static func sort(_ nums: [Int]) -> [Int] {
        var results:[Int] = []
        let maxItem = nums.max() ?? 0
        let semaphore = DispatchSemaphore(value: 0)
        let dTime = 0.05
        let accessQueue = DispatchQueue(label: "org.sadun.sortIsolation", qos: .default, attributes: [.concurrent], autoreleaseFrequency: .inherit)
        
        self.dispatch(after: Double(maxItem + 1) * dTime) { semaphore.signal() }
        nums.forEach { number in
            self.dispatch(after: Double(number) * dTime) {
                accessQueue.sync(flags: [.barrier]) {
                    results.append(contentsOf: [number])
                }
            }
        }
        let _ = semaphore.wait(timeout: DispatchTime.distantFuture)
        return results
    }
}

extension Array {
    // Scramble array members
    func scramble() -> [Iterator.Element] {
        var collection = self
        let elementCount = collection.count
        for offset in 0 ..< (elementCount - 1) {
            #if os(Linux)
                let r = offset + Int(rand() % (numericCast(elementCount - offset)))
            #else
                let r = offset + Int(arc4random_uniform(numericCast(elementCount - offset)))
            #endif
            guard r != offset else { continue }
            swap(&collection[offset], &collection[r])
        }
        return collection
    }
}

let array = Array(1...20).scramble()
print(array)
print(SleepSort.sort(array))