LeetCode——007 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: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

Solution:

Flip a character integer with
the highest value of [-2 ^ 31--2] ^ 31-1 32-bit system, since int type values range -2147483648 to 2147483647,

int reverse(int x) {
    int rev = 0;
    while (x != 0) {
        int pop = x % 10;
        x /= 10;
        if (rev > INT_MAX / 10 || (rev == INT_MAX / 10 && pop > 7)) return 0;
        if (rev < INT_MIN / 10 || (rev == INT_MIN / 10 && pop < -8)) return 0;
        rev = rev * 10 + pop;
    }
    return rev;
}

    class Solution {
public:
    int reverse(int x) {
        int res = 0;
        while (x != 0) {
            if (abs(res) > INT_MAX / 10) return 0;
            res = res * 10 + x % 10;
            x /= 10;
        }
        return res;
    }
};