for

• 문자열 보간법을 잘 활용하자

import Foundation
let number = Int(readLine()!)!

for i in 1...9 {
    print("\(number) * \(i) = \(number*i)")
}

• readline()받는 법 정리

let line = readLine()!
let intArr = line.components(separatedBy: " ").map({Int($0)!})

let line = readLine()!
let stringArr = line.components(separatedBy: " ").map({String($0)!})

let stringToInt = Array(readLine()!).map({Int(String($0))!})

• BOJ Tip
  https://www.acmicpc.net/blog/view/55
  https://www.acmicpc.net/blog/view/70

---

15552

15552
fread를 활용하라는데
@inline(__always)라구요?
무슨 말인지 모르겠는데요?

import Foundation
final class FileIO {
    private let buffer:[UInt8]
    private var index: Int = 0

    init(fileHandle: FileHandle = FileHandle.standardInput) {
        buffer = Array(try! fileHandle.readToEnd()!)+[UInt8(0)] // 인덱스 범위 넘어가는 것 방지
    }

    @inline(__always) private func read() -> UInt8 {
        defer { index += 1 }
        return buffer[index]
    }

    @inline(__always) func readInt() -> Int {
        var sum = 0
        var now = read()
        var isPositive = true

        while now == 10
                || now == 32 { now = read() } // 공백과 줄바꿈 무시
        if now == 45 { isPositive.toggle(); now = read() } // 음수 처리
        while now >= 48, now <= 57 {
            sum = sum * 10 + Int(now-48)
            now = read()
        }

        return sum * (isPositive ? 1:-1)
    }

    @inline(__always) func readString() -> String {
        var now = read()

        while now == 10 || now == 32 { now = read() } // 공백과 줄바꿈 무시
        let beginIndex = index-1

        while now != 10,
              now != 32,
              now != 0 { now = read() }

        return String(bytes: Array(buffer[beginIndex..<(index-1)]), encoding: .ascii)!
    }

    @inline(__always) func readByteSequenceWithoutSpaceAndLineFeed() -> [UInt8] {
        var now = read()

        while now == 10 || now == 32 { now = read() } // 공백과 줄바꿈 무시
        let beginIndex = index-1

        while now != 10,
              now != 32,
              now != 0 { now = read() }

        return Array(buffer[beginIndex..<(index-1)])
    }
}
let fIO = FileIO()
let n = fIO.readInt()
var str = ""
for _ in 0..<n {
    str += "\(fIO.readInt() + fIO.readInt())\n"
}
print(str)

---

2742

2742
for문 거꾸로 찍기

import Foundation

let line = readLine()!
let intVal = Int(line)!

for i in stride(from: intVal, to: 1, by: -1) {	//to가 0까지해야 5 4 3 2 1 이 나온다.
    print("\(i)")
}

stride 정리

stride(from:1, to:5, by:2)       // open range..5 불포함 1,3 까지만
stride(from:1, through:5, by:2)  // closed range..5 포함 1,3,5까지

---

2438

2438
별찍기
String(repeating: count: ) 요런 메서드가 있다

import Foundation

let line = readLine()!
let intVal = Int(line)!

for i in 1 ... intVal {
    print(String(repeating: "*", count: i))
}

배열 초기화에 자주 쓴다
[Int](repeating: count: )
[[Int]](repeating: [Int](repeating: count: ), count: )