LeetCode 7 Reverse Integer

题目：

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.

注意Note里的内容。反转前的范围为 [−2³¹,  2³¹ − 1]，即 [-2147483648, 247483647]，输入的值一定在这个范围内，但反转后可能超出这个范围，故需要用long保存结果，避免溢出得到错误结果，并判断反转后的值是否超出范围，超出则返回0。

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

PS：不需要对输入x的符号进行判断分别处理，因为java的取模得到的结果符号与被除数相同。