小数を探す(Lv.2)

に答える

import Foundation

func solution(_ numbers:String) -> Int {
    let numArr = numbers.map { Int(String($0))! } // [Int] 형으로 변환
    var resultArr = Set<Int>()
    Recursive(numArr, [], &resultArr)
    
    return resultArr.count
}

func Recursive(_ numArr: [Int], _ numbers: [Int], _ resultArr: inout Set<Int>) {
    for (i, num) in numArr.enumerated() {
        var newNumArr = numbers
        newNumArr.append(num)
        
        var assembleNum = 0
        for (j, num) in newNumArr.enumerated()  {
            assembleNum += Int(pow(Double(10), Double(j))) * num
        }
        
        // 소수 판별
        if isPrime(assembleNum) {
            resultArr.update(with: assembleNum)
        }
        
        var arr = numArr
        arr.remove(at: i)
        Recursive(arr, newNumArr, &resultArr)
    }
}

// 소수 체크
func isPrime(_ num: Int) -> Bool {
    if num == 0 {
        return false
    } else if num < 4 {
        return num == 1 ? false : true
    }
    
    for i in 2...Int(sqrt(Double(num))) {
        if num % i == 0 { 
            return false 
        }
    }
    
    return true
}

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