9. Palindrome Number, palindrome

9. Palindrome Number, palindrome

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

 

Some hints:

Cocould negative integers be palindromes? (Ie,-1)

If you are thinking of converting the integer to string, note the restriction of using extra space.

You cocould also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How wocould you handle such case?

There is a more generic way of solving this problem.

 

 

 

 1 class Solution: 2     def isPalindrome(self, x): 3         """ 4         :type x: int 5         :rtype: bool 6         """ 7         if x < 0: 8             return False 9         elif x < 10:10             return True11         t = x12         n = 013         while t > 0:14             n += 115             t = t // 1016         for i in range(n // 2):17             lnum = (x // (10 ** (n-i-1))) % 1018             rnum = (x // (10 ** i) ) % 1019             if lnum != rnum:20                 return False21         return True

Determines whether the two ends are equal based on the number of digits.