9. Palindrome Number

Leetcode link for this question

Discription:

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

click to show spoilers.

Some hints:
Could negative integers be palindromes? (ie, -1)

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

You could also try reversing an integer. However, if you have solved the problem “Reverse Integer”, you know that the reversed integer might overflow. How would you handle such case?

There is a more generic way of solving this problem.

Analyze:

Code 1:

class Solution(object):    def isPalindrome(self, x):        """        :type x: int        :rtype: bool        """        if x<0:            return False        for i in range(len(str(x))):            if str(x)[i]==str(x)[len(str(x))-i-1]:                continue            else:                return False        return True

Submission Result:

Status: Accepted
Runtime: 392 ms
Ranking: beats 4.18%

Code 2:

class Solution(object):    def isPalindrome(self, x):        """        :type x: int        :rtype: bool        """        if x<0:            return False                st=str(x)        le=len(st)        for i in range(le):            if st[i]==st[le-i-1]:                continue            else:                return False        return True

Submission Result:

Status: Accepted
Runtime: 292 ms
Ranking: beats 50.4%

Code 3:

class Solution(object):    def isPalindrome(self, x):        """        :type x: int        :rtype: bool        """        if x<0:            return False        st=str(x)        le=len(st)        for i in range(le/2+1):            if st[i]==st[le-i-1]:                continue            else:                return False        return True

Submission Result:

Status: Accepted
Runtime: 264 ms
Ranking: beats 80.18%