7. Reverse Integer（翻转整数）

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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 hold integers within the 32-bit signed integer range. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

 

 

 

 

 

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

 

 

 

用的是Python 转换成str ,然后翻转，需要注意

1.翻转之后如果溢出，输出0

 

class Solution:

    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        neg = x<0
        res = int(''.join(str(abs(x))[::-1]))
        if res > 2**31:
            res = 0
        if neg:
            res = -res
        return res