leetcode题目9：回文数

题目描述

判断一个整数是否是回文数。回文数是指正序（从左向右）和倒序（从右向左）读都是一样的整数。
示例：

输入: 121
 输出: true

解法

解法一：数字转字符串

class Solution:
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        if x < 0:
            return False
        else:
            y = str(x)[::-1]
            if y == str(x):
                return True
            else: 
                return False

解法二：纯数学计算

class Solution:
    def isPalindrome(self, x: int) -> bool:
        if x>=0:
            y = self.inverse(x)
            print(f"y:{y}")
            if y == x:
                return True
            else:
                return False
        else:
            return False
        
    def inverse(self, num):
        i = 0
        num1 = num
        while True:
            if num1//10==0:
                break
            i += 1
            num1 = num1//10
        sum = 0
        while i>= 0:
            sum = sum + (num%10) * (10**i)
            num = num // 10
            i = i -1
        return sum