7. Reverse Integer

Description

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: [ $-2^{31}, 2^{31} -1$]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

code

class Solution {
    public int reverse(int x) {
        int res = 0;

        while (x != 0) {
            int tail = x % 10;
            int newNum = res * 10 + tail;
            if ((newNum - tail) / 10 != res) {
                return 0;
            }
            res = newNum;

            x /= 10;
        }
        return res;
    }
}