https://leetcode.com/problems/reverse-integer/

這一題很簡單，需要注意檢查越界的程式碼。以下是C++和python的實現。

struct Solution {
	int reverse(int x) {
		long long sum = 0;
		for (; x; x = x / 10) { 
			sum = sum * 10 + x % 10; 
			if (sum > INT_MAX || sum < INT_MIN) 
				return 0; 
		} 

		return sum;
	} 
};

class Solution:
    def reverse(self, x):
        num = abs(x)
        sum = 0
        while num != 0:
            sum = sum * 10 + num % 10;
            num = int(num/10);
            if sum > (2**31-1) or sum < (-2**31):
                return 0

        if x > 0:
            return sum

        return -sum