leetcode 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.

 

 1 class Solution {
 2 public:
 3     int reverse(int x) {
 4         int rev = 0;
 5         while (x != 0) {
 6             int pop = x % 10;
 7             x /= 10;
 8             if (rev > INT_MAX / 10 || (rev == INT_MAX / 10 && pop > INT_MAX % 10))
 9                 return 0;
10             if (rev < INT_MIN / 10 || (rev == INT_MIN / 10 && pop < INT_MIN % 10))
11                 return 0;
12             rev = rev * 10 + pop;
13         }
14         return rev;
15     }
16 };