[프로그래머스]이모티콘 할인행사(Swift) - DFS

import Foundation

func solution(_ users:[[Int]], _ emoticons:[Int]) -> [Int] {
    var finalSaleCount: Int = -1
    var finalEmoticonPlusCount: Int = -1
    let dicountRates: [Int] = [10, 20, 30, 40]
    let users = users.sorted(by: { $0[0] > $1[0] })
    
    // 할인율 조합 dfs
    func dfs(arr: [Int], discountRates: [Int]) {
        
        // 할인율 조합의 count == 이모티콘의 count
        if arr.count == emoticons.count {
            // 할인율 조합으로 판매금액, plus 수 계산해서 업데이트
            countWithRates(with: arr)
            return
        }
        
        for r in discountRates {
            dfs(arr: arr + [r], discountRates: discountRates)
        }
    }
    
    func countWithRates(with arr: [Int]) {
        var saleCount: Int = 0
        var emoticonPlusCount: Int = 0
 
        for u in users {
            var sum: Int = 0
            for (i, r) in arr.enumerated() {
                if u[0] <= r {
                    sum += Int(Double(emoticons[i]) * Double(100 - r) * 0.01)
//                    sum += Int(Double(emoticons[i]) * (Double(100 - r) / 100))
                }
            }
            
            if sum >= u[1] {
                emoticonPlusCount += 1
            } else {
                saleCount += sum
            }
        }
        
        if emoticonPlusCount > finalEmoticonPlusCount {
            finalEmoticonPlusCount = emoticonPlusCount
            finalSaleCount = saleCount
        } else if emoticonPlusCount == finalEmoticonPlusCount {
            finalSaleCount = finalSaleCount > saleCount ? finalSaleCount : saleCount
        }
    }
    
    dfs(arr: [], discountRates: dicountRates.filter { $0 >= users.last![0] })
    
    return [finalEmoticonPlusCount, finalSaleCount]
}

소숫점 오차 발생할 수 있어서 나누기 조심해야한다.

sum += Int(Double(emoticons[i]) * Double(100 - r) * 0.01)
sum += Int(Double(emoticons[i]) * (Double(100 - r) / 100))

• https://school.programmers.co.kr/questions/42440