9. Palindrome Number #

Problem Statement: #

Given an integer x, return true if x is palindrome integer.

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

• For example, 121 is a palindrome while 123 is not.

Example 1: #

Input: x = 121
Output: true
Explanation: 121 reads as 121 from left to right and from right to left.

Example 2: #

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

Constraints: #

• -231 <= x <= 231 - 1

Follow up: Could you solve it without converting the integer to a string?

Solution: #

public static boolean isPalindrome(int x) {
  if (x < 0 || x % 10 == 0 && x != 0)
    return false;
  int reverseNum = 0;
  while (x > reverseNum) {
    reverseNum = reverseNum * 10 + x % 10;
    x /= 10;
  }
  return x == reverseNum || x == reverseNum / 10;
}

... #