문제 링크 (opens new window)

문제

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.

Assume the environment does not allow you to store 64-bit integers (signed or unsigned).

Example 1:

Input: x = 123
Output: 321
Example 2:

Input: x = -123
Output: -321
Example 3:

Input: x = 120
Output: 21

Constraints:

-231 <= x <= 231 - 1

풀이

1. 자릿수 하나씩 돌면서 결과값에 더해주기
2. 32비트 정수형을 넘어서면 안되므로 Int.max와 비교

class Solution {
    func reverse(_ x: Int) -> Int {
        var array: [Int] = []
        var result = 0

        for char in String(abs(x)) {
            let value = Int(String(char))!
            array.append(value)
        }

        for (index, i) in array.enumerated() {
            let tens = Int(pow(Double(10), Double(index)))
            result += tens * i

            if result > Int32.max {
                return 0
            }
        }

        return x < 0 ? -result : result
    }
}