[7]Reverse Integer

Reverse digits of an integer.

Example1: x = 123, return 321 Example2: x = -123, return -321

思路

除了用除法解出每一位以外，另一种方法就是将整型数据转为字符串，反转后再转成整型。

Code

Python

class Solution(object):
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        result = int(str(x)[::-1]) if x >= 0 else int('-'+str(x)[1:][::-1])
        return result if result <= 2147483647 and result >= -2147483648 else 0

Runtime: 75ms

Java

public class Solution {
    public int reverse(int x) {
        long sum = 0;
        while (x>0)
        {
            sum = sum*10 + x%10;
            x = x/10;
            if(x == 0)
                if(sum>java.lang.Integer.MAX_VALUE)
                return 0;
                else 
                return (int)sum;
        }
        while (x<0)
        {
            sum = sum*10 - x%10;
            x = x/10;
            if(x == 0)
                if(sum>java.lang.Integer.MAX_VALUE)
                return 0;
                else
                return (int)-sum;
        }
        return x;
    }
}