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9. Palindrome Number 👍

  • Time: $O(\log x)$
  • Space: $O(1)$
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class Solution {
 public:
  bool isPalindrome(int x) {
    if (x < 0)
      return false;

    long reversed = 0;
    int y = x;

    while (y > 0) {
      reversed = reversed * 10 + y % 10;
      y /= 10;
    }

    return reversed == x;
  }
};

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class Solution {
  public boolean isPalindrome(int x) {
    if (x < 0)
      return false;

    long reversed = 0;
    int y = x;

    while (y > 0) {
      reversed = reversed * 10 + y % 10;
      y /= 10;
    }

    return reversed == x;
  }
}

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class Solution:
  def isPalindrome(self, x: int) -> bool:
    if x < 0:
      return False

    rev = 0
    y = x

    while y:
      rev = rev * 10 + y % 10
      y //= 10

    return rev == x

var isPalindrome = function(x) {
  if (x < 0 || (x % 10 === 0 && x !== 0)) return false;
  let rev = 0;
  while (x > rev) {
    rev = rev * 10 + (x % 10);
    x = Math.trunc(x / 10);
  }
  return x === rev || x === Math.trunc(rev / 10);
};
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