Reverse Integer

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.

int reverse(int x) {
    int i = 0;
    int y = 0;
    __int64_t sum = 0;
    while(x != 0)
    {       
        i++;
        y = x % 10;
        if(i == 1 && y == 0)
        {
            continue;
        }
        sum = sum * 10 + y;
        if (sum > (pow(2, 31) - 1) || sum < (-pow(2, 31)))
        {
            return 0;
        }
        x /= 10;
    }
    return sum;
}

 

 需要注意的问题就是翻转的数据有可能会超出int类型的范围，所以用了__int64_t(-2^63 ~ 2^63-1)存储翻转的数据，用以比较反转的数据是否在int类型范围内