当处理非常大的数组(比如75000个样本)时,removeSubrange
函数是否足够快?或者我应该用其他更快的方法。
我可以用两种方式使用removeSubrange
,如下所示。计算时间有区别吗,特别是对于大样本。
import UIKit
var xt1 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
var xt2 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
xt1.removeSubrange(ClosedRange(uncheckedBounds: (lower: 7, upper: 9)))
xt2.removeSubrange(7...9)
print("Method 1:", xt1)
print("Method 2:", xt2)
最佳答案
从文档removeSubrange
。
复杂度:O(n),其中n是集合的长度。
这么小的尺寸。
var x = Array(repeating: "yes", count: 750000)
我用布拉德·拉森的代码来测量:
func timeElapsedInSecondsWhenRunningCode(operation: ()->()) -> Double {
let startTime = CFAbsoluteTimeGetCurrent()
operation()
let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
return Double(timeElapsed)
}
所以让我们试着测量一下。
timeElapsedInSecondsWhenRunningCode {
x.removeSubrange(4543...72000)
}
需要0.03秒
现在你可以做一些测量并找出答案。
这是一个完整的代码,它将执行32次迭代来测量随机范围内的性能。
var x = Array(repeating: "yes", count: 750000)
func timeElapsedInSecondsWhenRunningCode(from: Int, to: Int, operation: ()->()) -> Double {
let startTime = CFAbsoluteTimeGetCurrent()
operation()
let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
return Double(timeElapsed)
}
struct Test {
var range:(Int, Int)
var time:Double
}
var mesurments = [Int:Test]()
for i in 0...32 {
let from = randomInt(min: 0, max: x.count/2)
let to = randomInt(min: from, max: x.count)
let z = x
let time = timeElapsedInSecondsWhenRunningCode(from: from, to: to, operation: {
x.removeSubrange(from...to)
})
x = z
mesurments[i] = Test(range: (from, to), time: time)
}
func randomInt(min: Int, max:Int) -> Int {
return min + Int(arc4random_uniform(UInt32(max - min + 1)))
}