[Swift] 프로그래머스150369 택배배달과 수거하기

import Foundation

func solution(_ cap:Int, _ n:Int, _ deliveries:[Int], _ pickups:[Int]) -> Int64 {
    
    var ans: Int64 = 0

    var d = 0
    var p = 0

    for i in stride(from: n-1, through: 0, by: -1) {
        d += deliveries[i]
        p += pickups[i]

        while d > 0 || p > 0 {
            d -= cap
            p -= cap
            ans += Int64(( i + 1) * 2)
        }
    }

    return ans
    
}