LeetCode009 Palindrome Number

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

Example 1:

Input: 121
Output: true

Example 2:

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

Follow up:

Coud you solve it without converting the integer to a string?

 

思路和之前的整数倒置差不多，倒置后与原数进行比较

<方法一>转成字符串，倒序输出：

class Solution(object):
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        if str(x) == str(x)[::-1]:
            return True
        else:
            return False

//   return str(x) == str(x)[::-1]   一行代码

<方法二>不转为字符串，计算倒置整数，进行比较

class Solution(object):
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        if x<0:
            return False

        if 0<=x<10:
            return True
        
        rx = x
        result = 0
        
        while x>=10:
            a = x % 10
            result = (result+a) * 10
            x = (x-a)/10
        result += x
        
        if result == rx:
            return True   
        else:
            return False