ReverseInteger.java

package leetcode;

/**
 * @author eko
 * @date 2018/10/22 10:24 AM
 *
 * Given a 32-bit signed integer, reverse digits of an integer.
 *
 * Example 1:
 *
 * Input: 123
 * Output: 321
 * Example 2:
 *
 * Input: -123
 * Output: -321
 * Example 3:
 *
 * Input: 120
 * Output: 21
 * Note:
 * Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
 */
public class ReverseInteger {
    public static void main(String[] args) {
        int testNum = new ReverseInteger().reverse(-2124);
        System.out.println(testNum);
    }

    public int reverse(int x) {
        long res = 0;
        while (x != 0) {
            res = res * 10 + (x % 10);
            x = x / 10;
            if (res > Integer.MAX_VALUE || res < Integer.MIN_VALUE) {
                return 0;
            }
        }

        return (int)res;
    }
}