LeetCode-7. Reverse Integer

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问题描述

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).

Constraints:

  • -231 <= x <= 231 - 1

解答

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/*
 * @Description: 7. Reverse Integer
 * @Author: libk
 * @Github: https://github.com/libk
 */
/**
 * @param {number} x
 * @return {number}
 */
const reverse = function (x) {
  let res = 0
  while (x !== 0) {
    let rem = x % 10
    x = ~~(x / 10) // 连续两次按位取反，将小数部分舍去
    res = res * 10 + rem
    if (res > Math.pow(2, 31) - 1 || res < Math.pow(-2, 31)) {
      return 0
    }
  }
  return res
}