README_EN.md

7. Reverse Integer

中文文档

Description

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.

Assume the environment does not allow you to store 64-bit integers (signed or unsigned).

 

Example 1:

Input: x = 123
Output: 321

Example 2:

Input: x = -123
Output: -321

Example 3:

Input: x = 120
Output: 21

Example 4:

Input: x = 0
Output: 0

 

Constraints:

• -231 <= x <= 231 - 1

Solutions

Python3

class Solution:
    def reverse(self, x: int) -> int:
        y = int(str(abs(x))[::-1])
        res = -y if x < 0 else y
        return 0 if res < -2**31 or res > 2**31 -1 else res

Java

class Solution {
    public int reverse(int x) {
        long res = 0;
        while (x != 0) {
            res = res * 10 + (x % 10);
            x /= 10;
        }
        return res < Integer.MIN_VALUE || res > Integer.MAX_VALUE ? 0 : (int) res;
    }
}

C++

class Solution {
public:
    int reverse(int x) {
        long long ans = 0;
        while (x) {
            ans = ans * 10 + x % 10;
            x /= 10;
        }
        return ans < INT_MIN || ans > INT_MAX ? 0 : ans;
    }
};

JavaScript

/**
 * @param {number} x
 * @return {number}
 */
var reverse = function (x) {
    let res = 0;
    while (x) {
        res = res * 10 + (x % 10);
        x = ~~(x / 10);
    }
    return res < Math.pow(-2, 31) || res > Math.pow(2, 31) - 1 ? 0 : res;
};

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