7. Reverse Integer

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.

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/reverse-integer
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C++:

class Solution {
public:
    int reverse(int x) {
        int min = -2147483648, max = 2147483647;
        long long res = 0;
        while(x!=0) {
            res = res * 10 + x % 10;
            x = x / 10;
        }
        return res > max || res < min ? 0 : res;
    }
};

 C:

int reverse(int x){
    int min = -2147483648, max = 2147483647;
    long res = 0;
    while(x!=0) {
        res = res * 10 + x % 10;
        x = x / 10;
    }
    return res > max || res < min ? 0 : res;
}