NSDictionary をラップしてても O(1) になってる？ @swiftbot
import Foundation let native1M = [String: String](uniqueKeysWithValues: (1...1_000_000).map { ("\($0)", "\($0)") }) let cocoa1M = (native1M as NSDictionary) as! [String: String] let native2M = [String: String](uniqueKeysWithValues: (1...2_000_000).map { ("\($0)", "\($0)") }) let cocoa2M = (native2M as NSDictionary) as! [String: String] let n = 10 func measure(_ operation: () -> ()) { var sum: TimeInterval = 0 for i in 1...n { let start = Date.timeIntervalSinceReferenceDate operation() let end = Date.timeIntervalSinceReferenceDate let interval = end - start print("\(i): \(interval)") sum += interval } print("avg: \(sum / TimeInterval(n))") } let dictionaries: [(String, [String: String])] = [ ("Native 1M", native1M), ("Cocoa 1M", cocoa1M), ("Native 2M", native2M), ("Cocoa 2M", cocoa2M), ] for (name, dictionary) in dictionaries { print(name) measure { for i in 1...100 { _ = dictionary.keys.contains("\(i)") } } }