leetCode - Reverse Integer

문제

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

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풀이

const reverse = function (x) {
    const max = Math.pow(2, 31);
    let r = 0;
    while (x !== 0) {
        r = r * 10 + x % 10;
        if (r > max || r < -max) return 0;
        x = parseInt(x / 10);
    }
    return r;

};