<LeetCode>02_07_ReverseInteger

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 [-2^31, 2^31 - 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

Example 4:

Input: x = 0
Output: 0

작성코드

public class Solution {
    public int Reverse(int x) {
        string a = "";
        string c = "";

        if  (x > 0)
        {
            a = x.ToString();
        }
        else 
        {
            c += "-";
            a = (x*-1l).ToString();
        }

        string b = "";
        string answer = "";

        if (a.Length%2 != 0)
        {
            answer = answer + a[(a.Length/2)];
        }

        for (int i = 0; i<(a.Length/2); i++)
        {
            b = a[i] + b;
            c = c + a[a.Length-1-i];
        }


        if ((2147483647 < long.Parse(c+answer+b))||(long.Parse(c+answer+b) < -2147483648))
        {
            return 0;
        }

        return int.Parse(c+answer+b);
    }
}

배운점

• string으로 변환해 반복문 절반 줄이는 것보다 %를 이용한 반복이 훨씬 효율적.
• int32에서 벗어난 수는 * -1이 통하지 않아서, -1l로 써야한다.