Solved (JS): Determine whether an integer is a palindrome

readme.md

Palindrome Number

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

Example 1:

  Input: 121
  Output: true

Example 2:

  Input: -121
  Output: false
  Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.

Example 3:

  Input: 10
  Output: false
  Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

Follow up:

Coud you solve it without converting the integer to a string?

palindrome.js

const isPalindrome = (x) => {
  if (x < 0 || (x % 10 === 0 && x !== 0)) {
    return false;
  }
  
  return x === reverse(x);
};

const reverse = (num) => {
  let rev = 0;
  
  while (num != 0) {
    rev = rev * 10 + num % 10;
    num = parseInt(num / 10, 10);
  }
  
  return rev;
};

what is parseInt?

@7761962082 The parseInt() function parses a string argument and returns an integer of the specified radix (the base in mathematical numeral systems).

See more here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt

e.g.

const yearAsString = '2022';
const yearAsInt = parseInt(yearAsString, 10); // to base 10

console.log(yearAsInt); // => 2022