difficult：easy #728
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: [−$2^{31}$ , $2^{31}$ − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

解法

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

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