LeetCode - Palindrome Number (Java)

Determine whether an integer is a palindrome. Do this without extra space.

Thoughts

Problems related with numbers are frequently solved by / and %. No need of extra space is required. This problem is similar with the Reverse Integer problem.

    public boolean isPalindrome(int x) {
        //negative numbers are not palindrome
  if (x < 0)
   return false;
 
  // initialize how many zeros
  int div = 1;
  while (x / div >= 10) {
   div *= 10;
  }
 
  while (x != 0) {
   int left = x / div;
   int right = x % 10;
 
   if (left != right)
    return false;
 
   x = (x % div) / 10;
   div /= 100;
  }
 
  return true; 

}

Alternative Solution:
Credits go to Dev who suggested a recursive solution (if extra stack space does not count as extra space), which is pretty neat too.

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bool isPalindrome(int x, int &y) {   if (x < 0) return false;   if (x == 0) return true;   if (isPalindrome(x/10, y) && (x%10 == y%10)) {     y /= 10;     return true;   } else {     return false;   } } bool isPalindrome(int x) {   return isPalindrome(x, x); }

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