Algorithm
832. Flipping an Image
class Solution {
public int[][] flipAndInvertImage(int[][] A) {
for (int i = 0; i < A.length; i++) {
int count = A[i].length;
int j = 0;
for (j = 0; j < count / 2; j++) {
int left = A[i][j];
int right = A[i][count-1-j];
int swap = left;
left = right;
right = swap;
if (left == 1) {
A[i][j] = 0;
} else {
A[i][j] = 1;
}
if (right == 1) {
A[i][count-1-j] = 0;
} else {
A[i][count-1-j] = 1;
}
}
if (count % 2 == 1) {
if (A[i][j] == 1) {
A[i][j] = 0;
} else {
A[i][j] = 1;
}
}
}
return A;
}
}
由于没有学习过数据结构和算法，所以好多问题解决起来可能不是时间复杂度/空间复杂度相对优秀的，不过都是自己思考以后独立完成的，后续我会再单独梳理学习数据结构与算法，到时候把这些题目重新做一遍。
Review
翻译：
了解用户的设备信息通常被认为是分析App性能和衡量用户习惯的一种方式。然而，苹果官方并没有直接提供一个API来确定用户所使用的设备。基于此种场景，我们如何确定它是iPhoe X、iPhone 8、iPad还是Apple TV呢？
UIDevice类是获取当前设备信息的突破口。想要确定iOS设备的型号，我们可以通过model这一属性获取相关信息 -- model是一个用于描述型号的字符串，比如"iPhone"或者"iPod Touch"。
还有另外一个属性name可以告诉我们设备的名称。然而，这个名称通常是一个任意的字符串，比如"My iPhone XX"、"XX‘s iPad"；用户还可以通过"设置"-"通用"-"关于本机"-"名称"来修改。这种情况下，我们不能依赖这个name属性来获取特定的信息。
想要获取设备更多的详细信息，比如是iPhone XR还是iPhone XS，我们需要一些小技巧。众所周知，每一台iOS设备都有它自己的硬件标识，我们通常叫做设备型号或机器名称，比如"iPhone7，3"、"AppleTV5，3"。我们可以通过以下途径获取：
// https://stackoverflow.com/questions/26028918/how-to-determine-the-current-iphone-device-model
import SystemConfiguration
import UIKit
public extension UIDevice {
static let modelName: String = {
var systemInfo = utsname()
uname(&systemInfo)
let machineMirror = Mirror(reflecting: systemInfo.machine)
let identifier = machineMirror.children.reduce("") { identifier, element in
guard let value = element.value as? Int8, value != 0 else { return identifier }
return identifier + String(UnicodeScalar(UInt8(value)))
}
func mapToDevice(identifier: String) -> String {
#if os(iOS)
switch identifier {
case "iPod5,1": return "iPod Touch 5"
case "iPod7,1": return "iPod Touch 6"
case "iPhone3,1", "iPhone3,2", "iPhone3,3": return "iPhone 4"
case "iPhone4,1": return "iPhone 4s"
case "iPhone5,1", "iPhone5,2": return "iPhone 5"
case "iPhone5,3", "iPhone5,4": return "iPhone 5c"
case "iPhone6,1", "iPhone6,2": return "iPhone 5s"
case "iPhone7,2": return "iPhone 6"
case "iPhone7,1": return "iPhone 6 Plus"
case "iPhone8,1": return "iPhone 6s"
case "iPhone8,2": return "iPhone 6s Plus"
case "iPhone9,1", "iPhone9,3": return "iPhone 7"
case "iPhone9,2", "iPhone9,4": return "iPhone 7 Plus"
case "iPhone8,4": return "iPhone SE"
case "iPhone10,1", "iPhone10,4": return "iPhone 8"
case "iPhone10,2", "iPhone10,5": return "iPhone 8 Plus"
case "iPhone10,3", "iPhone10,6": return "iPhone X"
case "iPhone11,2": return "iPhone XS"
case "iPhone11,4", "iPhone11,6": return "iPhone XS Max"
case "iPhone11,8": return "iPhone XR"
case "iPad2,1", "iPad2,2", "iPad2,3", "iPad2,4":return "iPad 2"
case "iPad3,1", "iPad3,2", "iPad3,3": return "iPad 3"
case "iPad3,4", "iPad3,5", "iPad3,6": return "iPad 4"
case "iPad4,1", "iPad4,2", "iPad4,3": return "iPad Air"
case "iPad5,3", "iPad5,4": return "iPad Air 2"
case "iPad6,11", "iPad6,12": return "iPad 5"
case "iPad7,5", "iPad7,6": return "iPad 6"
case "iPad2,5", "iPad2,6", "iPad2,7": return "iPad Mini"
case "iPad4,4", "iPad4,5", "iPad4,6": return "iPad Mini 2"
case "iPad4,7", "iPad4,8", "iPad4,9": return "iPad Mini 3"
case "iPad5,1", "iPad5,2": return "iPad Mini 4"
case "iPad6,3", "iPad6,4": return "iPad Pro (9.7-inch)"
case "iPad6,7", "iPad6,8": return "iPad Pro (12.9-inch)"
case "iPad7,1", "iPad7,2": return "iPad Pro (12.9-inch) (2nd generation)"
case "iPad7,3", "iPad7,4": return "iPad Pro (10.5-inch)"
case "iPad8,1", "iPad8,2", "iPad8,3", "iPad8,4":return "iPad Pro (11-inch)"
case "iPad8,5", "iPad8,6", "iPad8,7", "iPad8,8":return "iPad Pro (12.9-inch) (3rd generation)"
case "AppleTV5,3": return "Apple TV"
case "AppleTV6,2": return "Apple TV 4K"
case "AudioAccessory1,1": return "HomePod"
case "i386", "x86_64": return "Simulator \(mapToDevice(identifier: ProcessInfo().environment["SIMULATOR_MODEL_IDENTIFIER"] ?? "iOS"))"
default: return identifier
}
#elseif os(tvOS)
switch identifier {
case "AppleTV5,3": return "Apple TV 4"
case "AppleTV6,2": return "Apple TV 4K"
case "i386", "x86_64": return "Simulator \(mapToDevice(identifier: ProcessInfo().environment["SIMULATOR_MODEL_IDENTIFIER"] ?? "tvOS"))"
default: return identifier
}
#endif
}
return mapToDevice(identifier: identifier)
}()
}
这个方法将设备类型输出为一个字符串，然而，并非是"iPhone X"或者"Apple TV4"。所以接下来我们需要将设备类型转换成更易读的字符串。想要做到这些，我们需要一个映射接口，可以在这里查阅到更详细的信息 Models - The iPhone Wiki
有了上面的映射定义，完整的实现如下
// https://stackoverflow.com/questions/26028918/how-to-determine-the-current-iphone-device-model
import SystemConfiguration
import UIKit
public extension UIDevice {
static let modelName: String = {
var systemInfo = utsname()
uname(&systemInfo)
let machineMirror = Mirror(reflecting: systemInfo.machine)
let identifier = machineMirror.children.reduce("") { identifier, element in
guard let value = element.value as? Int8, value != 0 else { return identifier }
return identifier + String(UnicodeScalar(UInt8(value)))
}
func mapToDevice(identifier: String) -> String {
#if os(iOS)
switch identifier {
case "iPod5,1": return "iPod Touch 5"
case "iPod7,1": return "iPod Touch 6"
case "iPhone3,1", "iPhone3,2", "iPhone3,3": return "iPhone 4"
case "iPhone4,1": return "iPhone 4s"
case "iPhone5,1", "iPhone5,2": return "iPhone 5"
case "iPhone5,3", "iPhone5,4": return "iPhone 5c"
case "iPhone6,1", "iPhone6,2": return "iPhone 5s"
case "iPhone7,2": return "iPhone 6"
case "iPhone7,1": return "iPhone 6 Plus"
case "iPhone8,1": return "iPhone 6s"
case "iPhone8,2": return "iPhone 6s Plus"
case "iPhone9,1", "iPhone9,3": return "iPhone 7"
case "iPhone9,2", "iPhone9,4": return "iPhone 7 Plus"
case "iPhone8,4": return "iPhone SE"
case "iPhone10,1", "iPhone10,4": return "iPhone 8"
case "iPhone10,2", "iPhone10,5": return "iPhone 8 Plus"
case "iPhone10,3", "iPhone10,6": return "iPhone X"
case "iPhone11,2": return "iPhone XS"
case "iPhone11,4", "iPhone11,6": return "iPhone XS Max"
case "iPhone11,8": return "iPhone XR"
case "iPad2,1", "iPad2,2", "iPad2,3", "iPad2,4":return "iPad 2"
case "iPad3,1", "iPad3,2", "iPad3,3": return "iPad 3"
case "iPad3,4", "iPad3,5", "iPad3,6": return "iPad 4"
case "iPad4,1", "iPad4,2", "iPad4,3": return "iPad Air"
case "iPad5,3", "iPad5,4": return "iPad Air 2"
case "iPad6,11", "iPad6,12": return "iPad 5"
case "iPad7,5", "iPad7,6": return "iPad 6"
case "iPad2,5", "iPad2,6", "iPad2,7": return "iPad Mini"
case "iPad4,4", "iPad4,5", "iPad4,6": return "iPad Mini 2"
case "iPad4,7", "iPad4,8", "iPad4,9": return "iPad Mini 3"
case "iPad5,1", "iPad5,2": return "iPad Mini 4"
case "iPad6,3", "iPad6,4": return "iPad Pro (9.7-inch)"
case "iPad6,7", "iPad6,8": return "iPad Pro (12.9-inch)"
case "iPad7,1", "iPad7,2": return "iPad Pro (12.9-inch) (2nd generation)"
case "iPad7,3", "iPad7,4": return "iPad Pro (10.5-inch)"
case "iPad8,1", "iPad8,2", "iPad8,3", "iPad8,4":return "iPad Pro (11-inch)"
case "iPad8,5", "iPad8,6", "iPad8,7", "iPad8,8":return "iPad Pro (12.9-inch) (3rd generation)"
case "AppleTV5,3": return "Apple TV"
case "AppleTV6,2": return "Apple TV 4K"
case "AudioAccessory1,1": return "HomePod"
case "i386", "x86_64": return "Simulator \(mapToDevice(identifier: ProcessInfo().environment["SIMULATOR_MODEL_IDENTIFIER"] ?? "iOS"))"
default: return identifier
}
#elseif os(tvOS)
switch identifier {
case "AppleTV5,3": return "Apple TV 4"
case "AppleTV6,2": return "Apple TV 4K"
case "i386", "x86_64": return "Simulator \(mapToDevice(identifier: ProcessInfo().environment["SIMULATOR_MODEL_IDENTIFIER"] ?? "tvOS"))"
default: return identifier
}
#endif
}
return mapToDevice(identifier: identifier)
}()
}
接下来你可以像下面这样来获取设备的model名称
let modelName = UIDevice.modelName
另一个建议是将映射函数放在服务端，今后iOS端只需要调用这个Api来实现model名称的转换。通过这种方式，当新设备启动的时候我们无需在本地更新映射接口，因为这个代码块又臭又长并且其修改极易出错。
Tip
Xcode10开始，创建代码块的路径为：Editor -> Create Code Snippet。
Share
What is the single most influential book every programmer should read? [closed]
