ReverseInteger.java

/**
 * Reverse digits of an integer.
 * <p>
 * Example1: x = 123, return 321
 * Example2: x = -123, return -321
 * <p>
 * Have you thought about this?
 * Here are some good questions to ask before coding. Bonus points for you if you have already thought through this!
 * If the integer's last digit is 0, what should the output be? ie, cases such as 10, 100.
 * Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer, then the reverse of 1000000003 overflows.
 * How should you handle such cases?
 * For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
 * <p>
 * Note:
 * The input is assumed to be a 32-bit signed integer. Your function should return 0 when the reversed integer overflows.
 * <p>
 * Accepted.
 */
public class ReverseInteger {

    public int reverse(int x) {
        if (x == 0) {
            return 0;
        }

        long result = 0;
        while (x != 0) {
            result = result * 10 + x % 10;
            x /= 10;
        }

        if ((result > 0 && result - Integer.MAX_VALUE > 0)
                || (result < 0 && result - Integer.MIN_VALUE < 0)) {
            return 0;
        }
        return (int) result;
    }

}