Reverse digits of an integer.
Example1: x = 123, return 321
Example2: x = -123, return -321

Note:
The input is assumed to be a 32-bit signed integer. Your function should return 0 when the reversed integer overflows.

Python

class Solution(object):
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        result = 0
        if x < 0:
            result = int('-' + str(x)[1:][::-1])
        else:
            result = int(str(x)[::-1])
        if result >= 2**31 - 1 or result <= - 2**31:
            return 0
        else:
            return result
        

Java

class Solution {
    public int reverse(int x) {
        String x_str = String.valueOf(x);
        char[] result_chars = x_str.toCharArray();
        char[] x_chars = x_str.toCharArray();
        if (x_chars[0] == '-'){
            for(int i = 1; i < x_str.length(); i ++){
                result_chars[i] = x_chars[x_str.length() - i];
            }
        }else{
            for(int i = 0; i < x_str.length(); i ++){
                result_chars[i] = x_chars[x_str.length() - i - 1];
            }
        }
        int result_int = 0;
        try {
            result_int = Integer.parseInt(String.valueOf(result_chars));
        } catch (NumberFormatException e) {
            e.printStackTrace();
        }
        return result_int;   
    }
}

参考答案

Python

class Solution:
    # @param {int} n the integer to be reversed
    # @return {int} the reversed integer
    def reverseInteger(self, n):
        if n == 0:
            return 0
            
        neg = 1
        if n < 0:
            neg, n = -1, -n
        
        reverse = 0
        while n > 0:
            reverse = reverse * 10 + n % 10
            n = n / 10
        
        reverse = reverse * neg
        if reverse < -(1 << 31) or reverse > (1 << 31) - 1:
            return 0
        return reverse

Java

public class Solution {
    /**
     * @param n the integer to be reversed
     * @return the reversed integer
     */
    public int reverseInteger(int n) {
        int reversed_n = 0;
        
        while (n != 0) {
            int temp = reversed_n * 10 + n % 10;
            n = n / 10;
            if (temp / 10 != reversed_n) {
                reversed_n = 0;
                break;
            }
            reversed_n = temp;
        }
        return reversed_n;
    }
}