Leetcode 筆記 :(9) Palindrome Number

tags: Leetcode

題目

Given an integer x, return true if x is palindrome integer.

An integer is a palindrome when it reads the same backward as forward. For example, 121 is palindrome while 123 is not.

Example 1:

Input: x = 121
Output: true

Example 2:

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

Example 4:

Input: x = -101
Output: false
 

Constraints:

-231 <= x <= 231 - 1

思考邏輯

1. 使用Python 那就當然要偷懶所以一開始就直接使用字串比對。

class Solution:
    def isPalindrome(self, x: int) -> bool:
        
        tmp = str(x)
        Palindrome = tmp[::-1]
        return tmp == Palindrome

2. 但是方法1好像太偷懶沒有思考到其他的，所以就乖乖用 mod 做計算

class Solution:
    def isPalindrome(self, x: int) -> bool:
        
        if x < 0:
            return False
        Palindrome = 0
        ori = x
        while(x != 0):
            tmp = x%10
            x = (x-tmp)/10
            Palindrome = Palindrome*10+tmp

        return ori == Palindrome