LeetCode T7 Reverse Integer

题目地址：

中文：https://leetcode-cn.com/problems/reverse-integer/
英文：https://leetcode.com/problems/reverse-integer/

题目描述：

Given a 32-bit signed integer, reverse digits of an integer.

Note:
Assume we are dealing with an environment that 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.

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

Constraints:

-2^31 <= x <= 2^31 - 1

思路：

因为题目限制在32位int的范围内，溢出输出0就可以，这里在运算过程中用long保存结果，然后与int的最大值和最小值进行对比就可以了。

其实模拟实现也可以。

题解：

class Solution {
    public int reverse(int x) {
        long temp = x;
        long temp_ = 0;
        int res;
        int flag = 1;
        if(x<0){
            flag = -1;
            temp = -temp;
        }
        while(temp!=0){
            temp_ *= 10;
            temp_ += temp%10;
            temp /= 10;
        }
        temp_ = temp_*flag;
        res = (int) temp_;
        if(flag==1 && temp_>Integer.MAX_VALUE) return 0;
        else if(flag==-1 && temp_<Integer.MIN_VALUE) return 0;
        else return res;
    }
}