reverse-integer.js

/**
 * Reverse Integer
 *
 * Given a 32-bit signed integer, reverse digits of an integer.
 *
 * Example 1:
 *
 * Input: 123
 * Output: 321
 *
 * Example 2:
 *
 * Input: -123
 * Output: -321
 *
 * Example 3:
 *
 * Input: 120
 * Output: 21
 *
 * Note:
 * Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range:
 * [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer
 * overflows.
 */

/**
 * @param {number} x
 * @return {number}
 */
const reverse = x => {
  const MAX = Math.pow(2, 31) - 1;
  const MIN = -Math.pow(2, 31);

  let res = 0;

  while (x !== 0) {
    res = res * 10 + (x % 10);
    x = parseInt(x / 10);

    if (res > MAX || res < MIN) {
      return 0;
    }
  }

  return res;
};

export { reverse };