白駿#1000:A+B

import Foundation

let line = readLine()!
let lineArr = line.split(separator: " ")

let a = Int(lineArr[0])!
let b = Int(lineArr[1])!

print(a + b)

import Foundation

let line = readLine()!
let lineArr = line.components(separatedBy: " ")

print(Int(lineArr[0])! + Int(lineArr[1])!)

import Foundation

var myName: String? = "sujilee" //myName은 옵셔널타입. "sujilee"로 초기화
var yourName: String? = nil //yourName은 옵셔널타입. nil로 초기화

if let name = myName, let friend = yourName {
    print("\(name) and \(friend)")
} else {
    print("some nil is bothering you")
}
//OUTPUT : some nil is bothering you

yourName = "sean" //nil이었던 yourName에 "sean" 값을 할당

if let name = myName, let friend = yourName {
    print("now \(name) and \(friend)")
}
//OUTPUT : noew sujilee and sean

 import Foundation

var line  = readLine() //readLine()은 String? 을 반환한다.

//lineArr에 대한 nil가드
if let lineArr = line?.split(separator: " ") {
    //a와 b에 대한 nil가드
    if let a = Int(lineArr[0]), let b = Int(lineArr[1]) {
        print(a + b)
    } else {
        print("case 2 : a b both nil")
    }
} else {
    print("case 1 : realine nil")
}